Transfer timeout in some linux machines

When flashing an image via MSD in Linux Mint 19.1, a FAIL.TXT file is generated with the error: "The transfer timed out.".

This issue was first reported on microbit devices (v0255) but can be replicated on a FRDM-K64F as well. So far, I have only been able to replicate this in Linux Mint 19.1, but some users have reported it on other Linux machines. (@microbit-carlos do you have more info on the other environments where this issue has appeared?)

I have narrowed down the issue as follows:
1. No issues in v0251. Can flash applications and no error is reported.
2. In v0252, there is an issue where the applications don't start after flashing (power cycle is needed) but no error is reported. This seems to have been introduced by #557, which interestingly caused the issue in #590.
3. In v0253, the issue in 2. was fixed by #592, but this also seems to have introduced this very specific timeout issue in some linux machines.

Some extra details on the issue:
-Tested in Ubuntu 16.04 and 20.04, and no issue is seen there.
-No issues with Windows or macOS.
-Small .hex files (24kB) don't have this issue, only with big .hex files (622kB as tested).

Start by reproducing the timeout while flashing a 622kB .hex file via MSD on Linux Mint 19.1, then compare behavior across versions v0251, v0252, and v0253. Read the changes associated with #557, #590, and #592 and compare results with Ubuntu 16.04/20.04, Windows, and macOS. Done means large transfers complete without generating FAIL.TXT while existing flashing behavior remains intact.

Written by the indexing model from the issue text.