И без разницы, запущен squid в этот момент или нет

Более того - ошибка воспроизводится только с отключенным дебагом. Включаешь отладку в squidmill - и всё становится чудно, за исключением забивания логов.

squidmill-2.7.0-alt2 -> sisyphus:

Sat Aug 30 2025 Paul Wolneykien <manowar@altlinux> 2.7.0-alt2
- Build without RPATH.
Thu Aug 28 2025 Paul Wolneykien <manowar@altlinux> 2.7.0-alt1
- Added a special test with no debug messages in daemon log (closes: 30142).
- Make SysV-init script to remove the socket file on stop (closes: 29894).
- Also, add support to print the test main log on success (PRINT_LOG_OK).
- Repeat all tests 10 times when building.
- Fixed/improved C-interface functions with Gambit 4.9.7.
- Allow to select tests (RUN_TESTS) and to repeat them (TEST_COUNT).
- Reworked tests + more tests.
- Reworked top-level exception handling.
- Rewrote the file-follow machinery (in the hope it's more stable now).
Fri Aug 22 2025 Paul Wolneykien <manowar@altlinux> 2.6.4-alt1
- Version 2.6.4.
- Replace SRFI-1 named getters with list-ref to avoid call
  to undefined symbols with some versions of Gambit (Fixes:
  OVE-20250822-0001).
- Run gsc with -warnings and check for undefined symbols.
- Fixed the extra log title in test output.
- Try to improve backtrace on error.
Thu Aug 21 2025 Paul Wolneykien <manowar@altlinux> 2.6.3-alt1
- Output SQL statements to the log with debug level > 1 only (-D -D).
- Print test logs on test fail (PRINT_LOG=1).
- Improved tests.
Tue Aug 19 2025 Paul Wolneykien <manowar@altlinux> 2.6.2-alt2
- Make [/var]/run/squidmill a ghost dir.
Tue Aug 19 2025 Paul Wolneykien <manowar@altlinux> 2.6.2-alt1
- Use squidmill.service unit to configure some fragile options
  (closes: 50276, 55654, 29894).