AX 2012 R2 repeated crashing when opening a PO or Supplier for multiple users

Anyone else having this problem?  We are using Windows 8.1 with AX2012R2CU7.  More than one user is experiencing regular crashing when opening either a PO, supplier, or project from the relevant 'all' list, or just upon opening up AX sometimes.  This happens in different live/test environments of AX.

things tried so far: -

.auc files removed

Reset form back to default without personalisation's (but we need them in to make the form useable!)

Kernel version is the same as Application version (6.2.1000.4051).

I saw another post with this problem but this was a year ago, and the solution was just to remove the .auc file (which seems to help temporarily).

any other ideas?

thanks