While I can't say much for mod removal or clients acting weird and doing such a thing possibly. I'd say when you aren't playing backup your modpacks and save files or install a mod that is known for scheduled backups if mods act odd sometimes, the world crashes or other issues.
For the clients acting weird I can't say much since I've only had that happen once and switched to MultiMC instead but that was Windows 10 rather than Twitch being the reason I couldn't use it because it 'worked at first' then thought it 'wasn't safe' (switched to MultiMC at this time of course) to use it to launch Minecraft through the Twitch Launcher for some reason, now works updates for the OS later Twitch works fine again. XD Never forgotten that time as strange as it was 2 years ago now when I was making videos on old mods histories and iterations for a series I was doing and had to switch launchers just to keep up with making them.
If I had to say anything about mods though it would be to not get them from dodgey/mod repost sites and only curseforge/Twitch if the mods act odd I guess, otherwise ask the mod developer what conflicts your having with the mod and they might be able to help out..
Niche Mod Finder/Acknowledger/Tester/Player. Fan of Datapacks, Rift 1.13/1.13.2 Mods, Fabric 1.14 Mods and interesting underrated or new 1.12.2 and below versions of mods. :) Testing 1.13.2 Forge and Fabric 1.14 mods mostly though.
I sometimes create the odd modpack or adventure map once an idea comes together.