OD light flashing and trans slips when cold

[floatbushpilot]

Hello Guys,
Not sure if this a repost but didn't find my answer yet...
My 97 E350 PSD is shifting erratically when cold (Montreal, Qc, Canada around 0 F) until the OD begins to flash. I assume that means the trans went on safe mode and increased the oil pressure inside.
At that time I stop, and restart the engine to reset the safe mode and the trans works fine and sweet the rest of the day (7 hours) and never the OD is flashing back again.
It did that the last 5 days.
I changed trans oil and filter 30 000 miles ago. (1 year)
Any guess ?
Thanks
Aymeric

97 E350 PSD stock 304 000 miles on it