Gear failure, corrects itself, then returns?

4,000 revs to get out of 1st, lost reverse and top gear. Drove 2000km home, corrected itself halfway home and proceeded to drive 6 months perfectly. Christmas 2023 problem returned. I left the car for 1-month, recharged the battery and test drove, working perfectly again. Need to fix problem, has anybody heard of this weird problem happening to someone else? How did they fix it? Does anybody know what this could be? Surely something mechanical could not suddenly work again, must be a computer issue?