LibreELEC 8.2.5 seems to have some sort of issue playing back Blu-ray .ISO files over SMB shares. Neither my HP Chromebox or Odroid C2 can play them smoothly running it (bone stock LE 8.2.5 install). On both the time from clicking on the .ISO in the file menu until the simple menu is displayed is 25-28 seconds. After selecting the title to play the throbber thingy comes up in the middle of the screen, slowly counts up to 100 and then playback starts. However, within about 40 seconds playback starts stuttering with dropped frames / gaps in the audio / stutters & pauses in the video.
In contrast the Raspberry Pi3 running LE 8.2.5 can play back the .ISO file fine. On it the simple menu pops up in about 14 seconds after clicking the .ISO. The Odroid C2 running wrxtasy's 32-bit 22.214.171.124 build of LE also can play them smoothly. With that HW/SW combo the simple menu pops up in 5 seconds after clicking the .ISO.
The same .ISO will play fine on all of these from a USB flash drive. The simple menu pops up instantly and playback is smooth from USB. The server is a Windows 10 Pro box with a 10Gb SFP+ connection to the switch and 1GbE from the switch to the boxes (except the Pi which only negotiates 100Mbit). I can get >100MB/sec copying the ISO file from the server to other PCs. Likewise I can copy data over the default SMB shares to the Chromebox and the C2 at >100MB/sec.
Forcing SMB 2 or SMB 3 from the LE menu didn't change the behavior with the C2. I didn't try that on the Chromebox.
wrxtasy suggested there is an underlying problem that's affecting multiple LE Kodi platforms and to start a thread here. I can provide logs files for troubleshooting if someone tells me what to log/do and which of the log files are desired.