Refresh fails first attempt (reason : data format) and success second attempt

I agree. I have a manual refresh in Power BI from MySQL which always fails first time with the input string in the wrong format problem. I go into Power Query editor and see the candy stripe error for the whole table. I click on another table and then click back on the problem table and it goes green (no changes made in the code). I close and apply and refresh and everything works just fine - on the third refresh(!) It seems as though Power BI thinks "this data is no good" (first time)  - "this data has a problem" (second time) - "Oh go on, I'll load it anyway" (third time). Surely this can't be the protocol?

MySQL is updated once a day by somebody else, and I'm the only one using it, so there's no conflicts or clashes. I've also ended parallel processing.

Ideas?

I also access the data from PowerQuery in Excel. Here I use VBA to load the data twice. First time each table (10) nearly always fails, so I have an error trap which runs the request again, which nearly always works.