I've been using Flexible OCI since day 1 on my 2016 CX-5. I did have some issues similar to yours after the first oil change and reset. The wrench indicator would pop up randomly from time to time although the oil life is at 100%. Only the PCM firmware update based on a TSB that fixed the problem since although my Flexible problem was different as described in the TSB. Never needs multiple resets.
BTW, I showed the TSB to service advisor and suggested him the PCM update to resolve the issue although the description of the problems is different from mine. He gladly accepted my suggestion and did the PCM update. In the end both sides were happy, as my Flexible problem got resolved, and he could charge Mazda NAO on the work they have done under warranty.
TSB 01-019/15: Engine Oil Flexible Maintenance Does Not Work 2014-2016 Mazda Vehicles
Bulletin No: 01-019/15 said:
DESCRIPTION
Some customer using "Flexible" setting for Oil Change in the maintenance monitor may notice that the oil change due notification will not work because of improper control logic of the PCM. This TSB is applicable for the following cases.
The oil change due notification does not come on, even after mileage exceeded 10,000 miles.
Oil life in the center display is still less than 40% even though the mileage exceeded 7,000 miles.
To display "Flexible" setting and "Oil life" on the center screen, select the "Applications" screen, "Maintenance", then "Oil Change" tab. For complete details, refer to the "MAINTENANCE MONITOR OPERATION PROCEDURE" in the Workshop Manual.
Customers having this concern should have their vehicle repaired using the following repair procedure.