mechanic indicates he is getting a frequency failure when the doors start to close, which initiates a reopen. if he makes close speed faster, it does not happen, any ideas.

What is your parameter "0" set at? (It should be 30hz)

That's weird. You would think that if the VF is failing it would be at all freq's. What about the basics, ie close signal, door scanner signal etc?

easy mistake to make, mistakenly adjusting parameter 0, which is Max speed close, not Hi speed close. so if you adjust parameter 0 below the value set in Hi speed close parameter 4, then when the doors start to close you get frequency failure, and the reopen relay will turn on, if you have wiring to the reopen circuit, which typically goes to your photo eye wiring, the doors will reopen. set parameter 0 back to 30, and then adjust hsc for correct speed, and all is well.
thanks JKH

Does anyone know what causes parameter checksum error with these operators? I had a new one that wasn't working right and was generating this fault, I changed a the board and all was good.

I've never seen the "checksum" error.