Serialization of 'Closure' is not allowed

Has anyone seen this in a php log, v8.5.12 site, php7.4?

No corresponding info in the concrete Log. I have a site generating a cluster of these every few days.

PHP Fatal error:  Uncaught Exception: Serialization of 'Closure' is not allowed in [no active file]:0
Stack trace:
#0 [internal function]: session_write_close()
#1 {main}
  thrown in [no active file] on line 0

@JohntheFish I had that issue when caching the autonav block. The explanation is in this article, under “Update for concrete 8.5.4”

Concrete had added a reference to the site tree in each autonav item and that contained a closure.

and also

Thank you.

  1. Looks similar, but in cache rather than session
  2. Looks very similar. This problem site is multilingual. I will add a cross reference in the Git incident. Serialization of 'Closure' is not allowed · Issue #11226 · concretecms/concretecms · GitHub