Hello!! New member here! 8D I was looking for a mod forum for my recent troubles with Skyrim and I seem to have found the right place >.<
I freely admit am not a complete pro at computers, but I have been using, tinkering and playing with mods for at least a year now and have run into my fair share of mod issues.
The tricky thing about a lot of mod EPSs is that you are asked to replace and rename certain files or folders in the Skyrim/Data/Scripts folders for them to work properly. This can sometimes become a problem even when deactivating/uninstalling some mods because depending on how they are written, the main Skyrim ESPs still work and interact with files of the same name as those that were re-written for the mod, and vice versa with the mod ESPs and Skyrim files. This causes scripting errors, mod install errors, twitchy gameplay, performance issues, and a host of other problems.
Make a back up copy of your Steam, Skyrim, Data AND Scripts Folder and back up the important files that if in the event this stuff happens, we can just go in and fix it. Yes I do my Steam folder as well to copy all my games. I personally have a 2TB external hard drive for back up storage purposes. I put all my manually backed up files in it. >.<
Yes mods do break, mafunction, even get abandoned, but we cant always control that. What we can control is how easily we can fix it.
Back up your files and save yourself time, energy and frustration.
Hope that helps in the future :)