BSOD on 2 of my first 4 prints?  

BSOD on 2 of my first 4 prints?

I've been 3D printing at home since 2016 on a QIDI Flash Forge clone and just upgraded to a 5-head Prusa XL. So far it's been a huge upgrade in every way except for software stability. My first print (the presliced Gear_Bearing gcode on flash drive) failed with a BSOD at 69%. It was garbage with stringing so I didn't try to restart it. I dropped PLA temp by 15 degrees, upgraded Prusa Slicer to 2.7.0-rc1 and my firmware to 5.1.0-alpha2 and printed a 200% articulated dragon in 3 colors and a practice gun for martial arts. Both of these printed perfectly, so I thought I was home free and tried a huge 3.5 day print, but it BSODed on me again just over halfway through. So my first question: is this par for the course or should these failures stop as the firmware is upgraded and is there anything I can do to stop it now?

My second question is about what happened when I tried to print to top of my huge print. I had to reset to get out of the BSOD screen and it didn't give me the nozzle position after it restarted, so I measured the height of the failed print and resliced to print the top with the intention of gluing it on later. When I tried to copy the gcode to the flash drive my computer said there was an error with the flash drive and asked if I wanted to repair it. I said yes and it wiped the drive. I copied my new gcode to the now empty flash drive and tried to print it, but when I inserted the flash drive the XL asked if I wanted to continue to old print. I said yes and it seems to have resumed where it left off. As a Prusa newbie, I thought all the print files were stored on the flash drive. If my flash drive got wiped how did the XL have my old print and know where to resume?