Why is my DI score volatile?

I have attempted all the GMAT club sectionals. The highest I got in DI was 77 with 67 the lowest. GMAT Club estimates my DI avg at 75.

I recently gave the OPE 1 and boy did I realise my timing is MESSED UP! I couldn’t attempt 2/21 Q questions (left them blank due to timing) and had to blind guess 2 in Q. But DI was much much worse. I blind guessed 7 out of 20 questions just to be able to finish the test and ultimately scored DI70?????

What is happening!! Please help if you know how to salvage this.