Downloading dataflash logfiles with Mission planner is very unreliable.

#### Issue details
Downloading dataflash logfiles with the Mission planner is very unreliable.
I normally connect a drone, go to the dataflsh logs download window, I normally get list of the logfiles, select one, press download and then one of two scenarios happen:
1) Downloading begins but somewhere in the middle it stops and MP disconnects from the drone. See the video here: [https://drive.google.com/file/d/1VmZi-VPUhwxAFszQOC-bJOrfvcCtLCaK/view?usp=sharing](url)
2) Downloading begins but when it's getting to the end (at about 98%) it jumps back to e.g. 20%, but here is the progress EXTREMELY slow (like 100x slower) so it's impossible to wait till the end.
Issue is happening more frequent on a new desktop PC I just bough twith a freshly installed Win11 professional.
I observed that H743 based FC works much worse, than F405 based FC.

#### Version
Mission planner 1.3.82 build 1.3.8979.17128, but tested also other vesions with the same issues.

#### Platform
[ ] All
[ ] AntennaTracker
[ X] Copter
[ ] Plane
[ ] Rover
[ ] Sub

#### Airframe type
Quad

#### Hardware type
Holybro H7 (worst one), speedybee F405 V4 (better results).

#### Logs
_Please provide a link to any relevant logs that show the issue_
https://drive.google.com/file/d/1-35QE13Y6BcNP_-btKWPW1J2MJSEC4DH/view?usp=sharing

Start by reproducing the failure in Mission Planner's dataflash log download window using the reported H743 and F405 hardware details. Review the linked video and Google Drive log, and trace the behavior around the disconnect and 98% progress reset. Done means the selected logfile downloads completely without disconnecting or becoming unusably slow.

Written by the indexing model from the issue text.