I have many hrs in Socata's.
Normally these slats come out pretty gently if all rollers and guides are properly lubricated.
We could fly all day with the slats gently moving in intermediate positions, just by changing airspeed by a knot or 2.
During normal operations they are completely out long before the stall happens, even in banking.
My guess :
Check the slats for FREE movement and listen to any abnormal noise from the guides, rollers or interconnecting system.
Disassemble and grease properly, and re-check the torque values of the rollers bolts. The rollers MUST roll freely.
What can happen with these older aircraft.
Some of the tubes wear off and have tread marks (grooves) in them where the rollers are. => Check, cross check and triple check. => The tube you are looking for is about 1inch in diameter.
Most of these older planes have wear marks and if the tubes are not replaced in time they "can" be the reason of the binding, and the slats coming out too late.