5th gear pops out?!

What’s goin on everyone. So I have a 2000 2.4l 2wd manual with 135,000ish miles on it. Nothing really wrong with it besides when I go and shift into 5th gear it pops right out?? It’ll stay in gear if I hold it in that position but I really have to hold it in. Had the tranny fluid changed. Changed the lil shifting seat thingy (the $15 part that goes right under the gear shift.) the only other times it’s hard to shift is on a cold morning into first which is pretty normal and when I puter in reverse I can feel it trying to catch until it finally does. If yall have any info or tips please help!!