E353: Nothing in register * from UnconditionalPaste glp in Windows

[Gary Johnson]

I use Ingo Karkat's UnconditionalPaste plugin a lot, especially the
glp command when I've copied something character-wise and want to
paste it line-wise.

I've noticed on Windows, that if I copy text from some other Windows
program and attempt to paste into gvim using the glp command, I get
this error message and no pasted text.

E353: Nothing in register *

However, pasting with the "*p command works fine.

I tried to troubleshoot the problem using the command

:debug normal glp

but when single-stepping through the plugin, there was no error and
pasting worked. I finally discovered that by setting a breakpoint
at line 32 of the UnconditionalPaste#Paste function, I could use the
continue command to run the plugin to that point and also use
continue to finish running the plugin without error. If I set the
breakpoint any later in that function, I would get the error after
the first continue. If I set the breakpoint any earlier in that
function, I would get the error after the second continue.

Here is line 32 of that function:

execute 'normal! "' . l:regName . (l:count ? l:count : '') . a:1

Since this behaved like a timing problem, I inserted this command
immediately before that line.

sleep 10m

With that, the glp command works fine. That's my workaround for
now.

The vimrc I used for troubleshooting contains only this line.

set clipboard^=unnamed

I'm using Vim 8.1.1244 and UnconditionalPaste 4.20 on Windows 10.
I've had no problems using glp on Linux, neither in gvim nor in
terminal vim.

Regards,
Gary