The 1003 error means that the tweaker failed to run the injected code as part of the explorer’s process.
This can be caused by an antivirus, which denies access to explorer due to security concerns.
Try whitelisting the tweaker.

That's a different issue. See here:

https://tweaker.userecho.com/communities/1/topics/165-remember-explorerfolder-order

See also my reply here:

https://tweaker.userecho.com/communities/1/topics/110-order-lost-when-updating

v5.6.2 is not the latest version. The latest stable version is 5.7, and the latest beta version is 5.7.0.3. Both should work with Windows 10 version 1903. Please update to one of these versions and see if that solves the problem.

What do you mean by "won't run"? Are you getting an error message? If yes, what's the exact message that you're getting?

Also, what's the version of your 7+ Taskbar Tweaker?

OK, I'll close the issue for now. Let me know if the issue comes back.

If you still experience the issue, you can try the linked guide, "Who the hell killed my process?", to find out why the tweaker is being terminated on your computer. Since I can't reproduce it on my computer, unfortunately I can't do much other than speculate.

Looks similar to the report of Rudolf Galan here:

https://rammichael.com/7-taskbar-tweaker-for-windows-10-october-2018-update#comment-10176

Please take a look at our conversation in the comments and see if the tips there help solve your problem.

See:
https://rammichael.com/7-taskbar-tweaker-for-windows-10-october-2018-update/comment-page-1#comment-10200

I assume that 7+ Taskbar Tweaker v5.7 fixes that. If not, please leave a comment.

Thank you for the extensive feedback. The short story is that saving the taskbar state is tricky to do correctly, and it's a complex piece of code, maintenance of which would be extra work for me. On the other hand, not many users requested this feature, and it's not going to be activated often (exiting/launching/updating the tweaker, explorer/tweaker crash, which should be rare in a routine workflow. Any other cases?).

Given the above, I still am reluctant to add and maintain such functionality as a part of 7+ Taskbar Tweaker.

looking at some other feedback here RaMMicHaeL, I have saw you said 1 year ago "I might have a piece of code lying somewhere which can save and restore the taskbar items order. Let me know if it can help, and I'll check if I can find it."

I do have something - you can find it here as a part of the open source Virtuoz virtual desktop utility. If it will help, I can look at implementing a standalone tool to save and restore the taskbar state, e.g. via a hotkey or a timer.