1988 Trail Boss shifter question

I’ve been having issues with my new to me ’88 250 4×4 popping out of high forward gear. I pulled out the gear box expecting the shift fork to be bent, but it looks fine as does the rest of the gear box. The only issue I found is some noisy bearings that I’ll replace.

Since the problem doesn’t appear to be in the gear box, the shifter and linkage adjustment are all that’s left. I noticed there are notches on the plate where the gear labels are. I’m wondering if the shift lever is supposed to have tension pushing it into the notch to help hold it in gear. I bought the machine last year, so I don’t know if it’s been altered over the years…