Someone who reported having the same problems (on the odroid forums) says it works with coreelec 9.0.1. (LibreELEC 9, odroid-c2: device does not get powered on by TV with CEC - ODROID)
Switched to coreelec 9.0.1 simply by putting the coreelec update into the Update folder an then did a reboot.
All Problems gone,
CEC Poweron works
no flashing white bars on the right side of the screen anymore
no sudden stops on live tv or recordings
no skip problems anymore
really satisfied 
Still an issue with v8.95.3 BETA.
TV is a Samsung T220HD
Powering on TV doesn't start the Odroic C2.
Libreelec CEC settings default exept
When the TV is switched off -> Power off
as I wrote, these things worked with LibreELEC (Krypton) 8.2.5 MR
Similar to here; Odroid_C2 8.90.006 no CEC Power on by connected TV - LibreELEC Forum
TV OFF powers off Odroid, but TV ON doesn't power on Odroid.
2x Odroid C2 - 64GB eMMC
created as ticket, since I was not enabled creating tickets before.
With LibreELEC-Odroid_C2.aarch64-8.2.5 power on the Odroid via CEC worked.
Since 8.90.00x powering on tv doesnt start the Odroid any more.
Powering off via shutdown menu from kodi also powers off the tv.
the log entries:
17:30:29.049 T:3723494256 DEBUG: CecLogMessage - >> 0f:36
17:30:29.049 T:3723494256 DEBUG: CecLogMessage - TV (0): power status changed from 'on' to 'standby'
17:30:29.049 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Broadcast (F): standby (36)
17:30:29.162 T:3723494256 DEBUG: CecLogMessage - >> 0f:36
17:30:30.849 T:3415397232 DEBUG: Thread JobWorker 3415397232 terminating (autodelete)
17:30:46.602 T:3723494256 DEBUG: CecLogMessage - >> 0f:32:64:65:75
17:30:46.602 T:3723494256 DEBUG: CecLogMessage - TV (0): power status changed from 'standby' to 'on'
17:30:46.602 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Broadcast (F): set menu language (32)
17:30:46.647 T:3723494256 DEBUG: CecLogMessage - >> 01
17:30:46.647 T:3723494256 DEBUG: CecLogMessage - << POLL: TV (0) -> Recorder 1 (1)
17:30:49.241 T:3723494256 DEBUG: CecLogMessage - >> 01:46
17:30:49.241 T:3723494256 DEBUG: CecLogMessage - << Recorder 1 (1) -> TV (0): OSD name 'Kodi'
17:30:49.241 T:3723494256 DEBUG: CecLogMessage - << 10:47:4b:6f:64:69
17:30:49.241 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Recorder 1 (1): give osd name (46)
17:30:49.484 T:3723494256 DEBUG: CecLogMessage - >> 01:8c
17:30:49.484 T:3723494256 DEBUG: CecLogMessage - << Recorder 1 (1) -> TV (0): vendor id Pulse Eight (1582)
17:30:49.484 T:3723494256 DEBUG: CecLogMessage - << 1f:87:00:15:82
17:30:49.484 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Recorder 1 (1): give device vendor id (8C)
17:30:49.812 T:3723494256 DEBUG: CecLogMessage - >> 01:a0:00:00:f0:23
17:30:49.812 T:3723494256 DEBUG: CecLogMessage - << 10:a0:00:00:f0:24:00:80
17:30:49.812 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Recorder 1 (1): vendor command with id (A0)
17:30:50.122 T:3723494256 DEBUG: CecLogMessage - >> 01:9f
17:30:50.122 T:3723494256 DEBUG: CecLogMessage - << Recorder 1 (1) -> TV (0): cec version 1.4
17:30:50.122 T:3723494256 DEBUG: CecLogMessage - << 10:9e:05
17:30:50.122 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Recorder 1 (1): get cec version (9F)
17:30:50.301 T:3723494256 DEBUG: CecLogMessage - >> 01:83
17:30:50.301 T:3723494256 DEBUG: CecLogMessage - << Recorder 1 (1) -> broadcast (F): physical address 1000
17:30:50.301 T:3723494256 DEBUG: CecLogMessage - << 1f:84:10:00:01
17:30:50.301 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Recorder 1 (1): give physical address (83)
17:30:50.647 T:3723494256 DEBUG: CecLogMessage - >> 0f:80:00:00:10:00
17:30:50.647 T:3723494256 DEBUG: CecLogMessage - Recorder 1 (1) was already marked as active source
17:30:50.647 T:3723494256 DEBUG: CecLogMessage - >> source activated: Recorder 1 (1)
17:30:50.647 T:3723494256 DEBUG: CecLogMessage - sending active source message for 'Recorder 1'
17:30:50.647 T:3723494256 DEBUG: CecLogMessage - << powering on 'TV' (0)
17:30:50.648 T:3723494256 DEBUG: CecLogMessage - << 10:04
17:30:50.648 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Broadcast (F): routing change (80)
17:30:50.851 T:3723494256 DEBUG: CecLogMessage - << Recorder 1 (1) -> broadcast (F): active source (1000)
17:30:50.851 T:3723494256 DEBUG: CecLogMessage - << 1f:82:10:00
17:30:51.021 T:3723494256 DEBUG: CecLogMessage - << Recorder 1 (1) -> TV (0): menu state 'activated'
17:30:51.021 T:3723494256 DEBUG: CecLogMessage - << 10:8e:00
17:30:51.341 T:3723494256 DEBUG: CecLogMessage - >> 0f:85
17:30:51.341 T:3723494256 DEBUG: CecLogMessage - >> 0 requests active source
17:30:51.341 T:3723494256 DEBUG: CecLogMessage - << Recorder 1 (1) -> broadcast (F): active source (1000)
17:30:51.341 T:3723494256 DEBUG: CecLogMessage - << 1f:82:10:00
17:30:51.341 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Broadcast (F): request active source (85)
17:30:51.511 T:3723494256 DEBUG: CecLogMessage - >> 01:8d:02
17:30:51.511 T:3723494256 DEBUG: CecLogMessage - << Recorder 1 (1) -> TV (0): menu state 'activated'
17:30:51.511 T:3723494256 DEBUG: CecLogMessage - << 10:8e:00
17:30:51.511 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Recorder 1 (1): menu request (8D)
17:30:51.711 T:3723494256 DEBUG: CecLogMessage - >> 01:1a:01
17:30:51.711 T:3723494256 DEBUG: CecLogMessage - << Recorder 1 (1) -> TV (0): deck status 'stop'
17:30:51.711 T:3723494256 DEBUG: CecLogMessage - << 10:1b:1a
17:30:51.711 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Recorder 1 (1): give deck status (1A)
17:30:51.851 T:3723494256 DEBUG: CecLogMessage - >> 01:8d:02
17:30:51.851 T:3723494256 DEBUG: CecLogMessage - << Recorder 1 (1) -> TV (0): menu state 'activated'
17:30:51.851 T:3723494256 DEBUG: CecLogMessage - << 10:8e:00
17:30:51.851 T:3723494256 DEBUG: CecLogMessage - >> TV (0) -> Recorder 1 (1): menu request (8D)
BR
Tom
