I believe your issue is MySQL attempting to encode an invalid UTF-8 byte sequence. I checked (even though it is obvious if you work with encoding/decoding UTF-8 on string sequences) and
\xD5ve is not a valid hex code for a UTF-8 character. I have no idea why that string is in one of your templates, but it is.
A partial guess is that upgrading to EE3 forced your encoding from Latin-1 (or something else) to UTF-8, and now it can't handle the invalid sequence. Or the new templates you are adding just plain have invalid UTF-8 sequences.
This is kind of a far out guess, but could be it. To test this, I would:
Backup your database. Preferably, don't run this on a production server, but only on a staging/local dev instance.
Attempt to find, and remove the violating byte sequence. I would do it in both your file template assets, as well as in their
To find a code sequence, I would log on to a server and navigate to your template group. This command is really handy:
grep -nr search\-string
You may have to try a few different versions to match it exactly (escaping charcters for grep):
grep -nr \\xD5ve
For your database, just use a
LIKE query on the
template_data column. Should do the trick:
SELECT * FROM exp_templates WHERE template_data LIKE "%\xD5Ve%";
Hrm, did I get that right? Been a million years since I had to write a query. Anyways, that is my current suggestion; find and remove invalid UTF-8 sequences from all of your templates, but start with the one.