Worksheets("xx").Activate - breaks macro

RandomPanda There's nothing you did to cause this. It is 100% the result of bad updates from Microsoft and has been affecting practically everyone since mid-December. Although Microsoft has claimed to resolve this issue in their February update, the fact that you and other people are still experiencing these issues suggests otherwise. There's a really good discussion thread that got a lot of attention back in December, where people have continued to share the ways in which they resolved the problem. The suggestion you might find most applicable for your situation was made by MKirsch, and can be viewed here: https://techcommunity.microsoft.com/t5/excel/excel-macros-disappear-from-xlsm-file/m-p/4040066/highlight/true#M218598 

By all means read through the entire thread, though, as there are other suggestions that indicate uninstalling the 64-bit version of Excel and reinstalling the 32-bit version will give you less grief moving forward (I have not tested this yet to verify it).