loop 8 short flashes of the green LED, according to PI5 documentation it means SDRAM failure
That indeed could be a RAM failure (BGA soldering maybe) or a power source issue... or something else. But a full debug log could provide more information. Just don't forget, there is many people using their RPi5 with LE without complains, so is a solid possibility to be something wrong at your setup. Another thing you can easy try, find a spare SD-card and install the latest LE13 nightly build (that's a nice thing in the RPi). Just to see if there is any difference. These nightly builds usually are stable for daily use. One last thing, all the RPi boards have only a tiny wifi antenna, so if you have any posibility, better use cable.