Cannot create the AMA sample mapper to play this clip

Hi all,

Am working in a project consisting entirely of AMA linked Prores LT material in version 6.0.3.3 and I regulary get the above error message which dissapears after a software re-start. This is now happening more requently however, (every 3/4 clips) and it's obvioulsy pretty disrupptive to keep re-starting the system. 

I can't find anything about what woild cause this specific issue with prores material so any help would be very much appreciated.

Best,

GK