I had repair work done, and now the transmission is acting up.

If you notice problems with your transmission right after other repair work has been done, call it to the attention of the technician or facility that performed the repair.  Occasionally, a problem may be inadvertently created during a repair.  But, don’t wait too long;   this “unintended consequence” should be investigated as soon as practical.  Logic dictates that if the transmission worked well before, it should after.  Just remember to use some diplomacy.