After upgrade to 3.3.11 -> PHP Warning: in file [ROOT]/vendor/s9e/text-formatter/src...

[wonder_wonder]

I have recently converted a forum vb 4.2.5 to phpbb 3.0.11.
After that conversion, I upgraded phpb 3.0.11 to 3.3.11 via cli.
After the upgrade I ran the repairer.

The following happens to me:

Every time I access the forum or the ACP, the first time I access I get these error lines above:

[phpBB Debug] PHP Warning: in file [ROOT]/vendor/s9e/text-formatter/src/Configurator/Helpers/TemplateLoader.php on line 33: DOMDocument::saveXML(): invalid character value
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/s9e/text-formatter/src/Configurator/Helpers/TemplateLoader.php on line 33: DOMDocument::saveXML(): string is not in UTF-8

After the second click, it no longer appears unless you delete cache.

I looked for info, I looked to see if it had bbcodes, there were two, when I went to delete them it told me:

AJAX error
Something went wrong with the request and the server returned an invalid reply.

The same thing indicates with Topic Icons and Smiles, but despite the error, if I go back it has removed them.

Any ideas?

Thank you and greetings.

Edit:
The reparser, some times, indicate this:

Warning: DOMDocument::loadXML(): Char 0xFFFE out of allowed range in Entity, line: 8 in /home/mydomain/cableold/phpbb3/vendor/s9e/text-formatter/src/Utils.php on line 161
PHP Warning: DOMDocument::loadXML(): PCDATA invalid Char value 65534 in Entity, line: 8 in /home/mydomain/cableold/phpbb3/vendor/s9e/text-formatter/src/Utils.php on line 161

And I haven't been able to capture it, but some r or R
I mention the R because in the search I have seen posts that referred to it.

Edit 2: Solved!
I've been dealing with this for a long time, and the sooner I post, the sooner I fix it... sorry...

The problem was that, in smiles, there was code with strange characters, by eliminating them, it was solved.