We've been running some custom properties from the Property Tab Builder for years, however yesterday, for no apparent reason the blank fields are now showing up as an 'ERROR!'

Heres the actually text links:

Normally, when theres nothing entered the fields are blank.

So, does anyone know why this has started to happen all of a sudden? When same part/drawing is opened on the other Solidwork 2016 SP5 PCs, the fields are blank.

This is affecting ALL old & new drawings & actually a big issues as I cant print or save the drawing until this is sorted.