Hmmm, ok my next suspicion is either your USB cable or the version or how you are running esptool.
How is your set up?
are you using windows, linux mac?
Have you updated your platform drivers ?
Have you tried another USB cable?
Are you using a USB hub in between?
My last suspicion is your core2.
It is windows 10 running kali on virtualbox. Idf 4.2, powered usb 3.0 hub.
I have been using the wrover kit, wroom, esp8266 and the core 1 grey without any troubles.
As the flash fails with the core2, simply changing to the core 1 gray completes successfuly.
Also I was able to erase the core2 using the windows esp32 flath tool many times.
Looks like in the new core2 the boot pin is not held low long enough to put it in bootloader mode in this virtualized setup.
Again... where the core2 fails a core1 gray does very well. I did not open them yet to spot the differences.