05 Nissan Altima 3.5 AT shifting issue

The problem started about a week ago when, when I pulled into a parking space and my car wouldn't go into park. The shifter would go into Neutral but not Reverse of park. I had my foot on the break but still it wont budge. I shut the engine off in N with the E-break on and then started it again. this time no issue. This has happened a few times since then. Then today it did the same thing but I could not get it to release. I had to pull the transmission lock cover and get out of park this way. Does anyone have any thoughts as to what could cause this and what I can do to fix it.

Thanks