prusa mk3 lcd displays f quotation

Sliced with PrusaSlicer 2.0.0, Printing on MK3S with Firmware v3.7.1.   This is only second print with this slicer/FW combination.  I don"t think the F? was there before but not absolutely sure.  It seems to be printing OK.

Check if the printer is thinking it has an MMU. The F? indenticates which filament is loaded. The question mark because it has no information about it.

I"ve the same isse from time to time, and another guy in the FB group too. My suggestion, it is caused from noise on the port where normally the MMU is connected, or an PWM, an fan. Maybe an bad powersupply or bad contact.

1) If you insert the SD card to the LCD panel, are you able to access it through the LCD? If not, you need new cables or just take a look at them if they are not damaged (mainly it gets damaged when anchoring to the threaded rods with zipties) so please check that and let me know.

2) The video is with connected heatbed right? If so, you definitely have something wrong with it, now let"s just check what. if you unmount it, and remove all the screws in the corners, are you able to see some damage where M3 washers were? If you plug it in to the printer (without the screws mounted), is it working properly? If so, you need new heatbed or you can do little trick by insulating the bottom copper plane from the washers until the new one arrives.

1.) I inserted the SD card as it came, and the LCD shows "no SD inserted" when i take it out and plug it back in. I dont have a card reader on hand at the moment to try it with actual data on it ?(If it doesnt already come with anything?)

2.) The heatbed lives! without the screws attached. I have a very nice blister on my finger for proof haha So i am about to try and use some heatproof plastic as washer (With the metal washers) to see if i can get it mounted and functioning with them. Is this something i screwed up during installation? i ask just so i can let a friend know to be careful when hes assembling his