Strange error, never seen before

I suddenly get tons of this error on my log.

2023-05-13 21:38:01.950 ERROR (MainThread) [aiohttp.server] Error handling request
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/aiohttp/web_protocol.py", line 433, in _handle_request
    resp = await request_handler(request)
  File "/usr/local/lib/python3.10/site-packages/aiohttp/web_app.py", line 504, in _handle
    resp = await handler(request)
  File "/usr/local/lib/python3.10/site-packages/soco/events_asyncio.py", line 138, in notify
    variables = parse_event_xml(content)
  File "/usr/local/lib/python3.10/site-packages/soco/events_base.py", line 104, in parse_event_xml
    value = from_didl_string(value)[0]
  File "/usr/local/lib/python3.10/site-packages/soco/data_structures_entry.py", line 31, in from_didl_string
    root = XML.fromstring(string.encode("utf-8"))
  File "/usr/local/lib/python3.10/xml/etree/ElementTree.py", line 1342, in XML
    parser.feed(text)
xml.etree.ElementTree.ParseError: not well-formed (invalid token): line 1, column 1015

From what it is caused?