I downloaded replay mod for 1.7.10 and it keeps crashing, showing the same player multiple times in the player overview, doesn't fully render and bugs out. I tried everything to fix this, deleting and re-installing Minecraft and changing forge version, nothing happened. However, when I downloaded 1.8.9 forge and 1.8.9 Replay everything was working fine. So my question is, why isn't replay mod working on 1.7.10.
There's quite a significant difference between 1.8 and 1.7.10 which is where most of the bugs come from.
1.7.10 isn't receiving much testing (because https://www.howoldisminecraft1710.today/) and for the same reason not much development time. I'd be happy to take PRs if there's some developer interested in improving 1.7.10 support (as is, I'm the only one working on all of the RM and 1.7.10 is all the way down on my todo list).
About 25% of all RM users (by downloads) are on 1.8.x, so there's a lot more testing happening there.
The 1.7.10 version mainly exists because the last time I tried to do the normal thing of dropping old versions, people weren't happy with that either.