BLOCSTACKED Non-existent strucure member Error

SOLVED

Hi,

Has anyone seen this error before or have any idea what the cause may be?

I have started getting this error every time I log in following a failed V12 Patch 22 upgrade. 

Everything looks OK in the console but the X3\TRA folder contains many error files:

Each of the error files refers to the same BLOCSTACKED error:

Any suggestions what may be causing this and how to go about fixing it?

Many thanks,

Martin