I have been revising an old plan view document and went to add text into the revision notes on the title block, the text was successfully added but then the previous text that was in the block disappeared. it was still on the drawing but not visible and isn't visible when i print. 

I‌f i zoom right into the document then the text appears but when i zoom out it disappears again.‌ 

T‌his happens whenever i try adding new text to the title block or if i copy and paste an existing text box to the title block‌.

I‌ have tried removing and re-adding the title block but i get the same issue.

A‌ny help gratefully received.‌