As Yami_ wrote: here:
The News section issue was fixed in Firefox 55:
Last bad: 2017-04-17
First good: 2017-04-18
Perhaps that helps to limit the number of culprits.
Also, i have seen a warning in the error console which looks rather strange:
Timestamp: 07.10.2018 13:11:43
Warning: Unexpected end of file while searching for length value for matched media condition.
Source File: from DOM
Repeats a lot of times when visiting the Gog main page