Slamming gears/reverse slam

Basically two days ago the problem started randomly after my girlfriend drove the car (she’s used to not putting her foot on the brake when shifting to R to Drive) so we think that might’ve been what caused it. Now when shifting from Park to Reverse (in any temperature) it’ll bang into gear but no delay. It will also slam into first gear/second and seems to slip a bit (sometimes) when shifting into third. The other gears seem to shift normally. I’ve seen lots of threads explaining many different causes for this problem and I’m not going to risk getting a new Valve Body for $500.00 if it won’t fix it for sure. Is there anyone that can give me some good tips on what to do and what might be causing this?