Excel issues with Sharepoint

Hello, 

Not sure if this is the best place to start - but I have been having some issues within the last 1-2 months with excel files & new modern SharePoint and was hoping maybe somebody could provide some pointers?

I have a weekly excel report with slicers and a data model that I upload to sharepoint on Mondays.  Usually by Tuesday or Wednesday, I get a notification lately that someone can't open it (error message literally says can't open with a red X) and then when I open it, all the slicers but one are gone.  This happens probably 1-2x per week.  Thankfully I keep my master files on my desktop, so it's easy to replace - but I have no idea why this has been happening.  I've tried changing the format of the file from .xlxs to .xlsm to see if that changes things, and I think that made it worse.  

So now it's back to .xlxs and still having the issues.  Any ideas / thoughts out there?

Thank you!