Another Mac crasing topic...but please help!

@HuitFerdinand  If your sims are going to travel, definitely add NRaas Traveler.  It won't help with the crashes you're currently seeing if they're not travel-related, but it will replace the travel transition with a version that's much more stable.  Considering supernaturals are in your game, NRaas Hybrid may be helpful too—it supports hybrid states but also fixes a few issues with single occult states.

I would also recommend NRaas MasterController for its option to reset the entire town (NRaas > Mc > Town Options > Reset Everything).  This can sometimes help with a crash that's repeating itself and is good for the overall health of your save.  If you don't want your sims reset too, there's a setting to exclude the active lot in Reset Everything, so you can run the command at night when your own sims are home.  You can also reset a single sim or lot if necessary, for example I had a repeated crash when my sims went to the hospital that was resolved by reseting that lot.  MC doesn't do anything on its own, so it's not going to change your experience in general.

Beyond that, it's hard to say what would help without any kind of pattern.  The crash when the sim gained a guitar skill point could be a one-off, it could be because the sim was playing when you loaded the save and something was stuck, it could be a total coincidence... it's difficult to say given how many ways this game can break.