It might pay to get a code reader on it & let us know what it tells you. Sounds like the transmission control computer is giving problems. Open it up & have a look for the obvious capacitor leakage problem with this one. These computers have a history of SMD chip resistors going open circuit, which is impossible to spot, but easy to measure with a multimeter. I've personally repaired hundreds of similar systems over the years.
crwdns2934105:0crwdne2934105:0
crwdns2934113:0crwdne2934113:0
crwdns2915270:0crwdne2915270:0
crwdns2889612:0crwdne2889612:0
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