At the end of 2019, some players found a nasty few bugs in v1.2. These were fixed in v1.3 and then finally in v1.4. The changelog for both updates can be found HERE.
These fixes will affect anyone using the Eternity source port or players who are using the original DOS executable. If you are playing in a different port (ie. GZDoom), then its very unlikely you'll run into any of the bugs in v1.2.
Also since it has been brought up a few times in various places, I'll address the re-release of Doom 64 with the new map pack. There have been some folks who want to see the new maps converted over to vanilla as an extra for this map pack. I think the idea is really cool and it is something I wouldn't mind doing if I get the chance. However since the game was re-released commercially very recently, I feel like I need to be extra careful and get permission to do such a thing. For the time being, I'm not making in immediate plans to convert the new maps over. But its something I'll keep in mind for the future.
Take care and thanks for playing!