The other part is probably the conductor plate. To replace it, the valve body must be removed, so you're looking at about 2-3 hours labor. IMHO, the conductor plate is the weakest link. The valve body may be the problem (I doubt it), but the only way to be sure is to know what fault codes are stored in the transmission. Can you get this information from your local tech? If so, let us know.

In the meantime, have the battery and charging system tested. Low voltage can cause a variety of issues. Keep us posted.