Edit: Oh I have just checked my PMI add $25 bounty for this issues solution. (Will paid by crypto)

And for those who still have this issue you can try next solution:
I had this issue too, FIRST Try to fix it simply by UNPLUG and PLUG the USB stick with freshly copied SammyGo

If not helps use this procedure:
1.) Connect your SammyGo USB stick
2.) Perform Factory reset from service menu, perform factory reset from normal menu (if have) - all resets possible
3.) install 0000 Firmware (search on forum or I have some)
4.) install 2126 Firmware (or perform auto-update if works)
5.) remove your SammyGo USB stick
if does not help:
6.) re-root your TV with SammyGo USB than remove your USB stick
last chance:
7.) manually delete all SammyGo files by SSH or FTP???