What causes the transmission to down-shift roughly on stopping? on 1998 Honda Accord

Car drives ok. Up-shifts smoothly but jerks when you come to a halt and it shifts into 1st.
Mounts are ok. Replaced "lock-up" sensor but problem persists.

3 answers 4 comments
Mounts are ok? Any engine movement when shifting from reverse to drive and viseversa? Upshift puts a different torque load on mounts as opposed to downshift! Engine will react differently. Have a mechanic test drive it.
The engine and transmission mounts were replaced with genuine Honda mounts.
The jerking occurs only when you come to a complete stop, not when it down-shifts while in motion.
Check engine light on? Does it feel like an engine skip or misfire while stopped in gear?
No check engine light. Engine runs smoothly all the time.
See next answer.
What is the idle speed at in park and in drive? Honda ATF in it? Check level with trans warmed up and engine shut off , on LEVEL surface. Next step would be to have trans monitored while test driving. How many miles on it & is it original trans?
My check engine light is on when this happens