Dump_log_update_in_place is set to true, but mnesia continues to copy table to temp file

I’m desperately struggling to force mnesia, called from elixir app, to stop creating temp files when it dumps transaction logs.
dump_log_update_in_place is set to true in config.exs and reads as true by :mnesia_monitor.get_env
But nothing helps - every time it dumps logs - it creates a temp file, copies table to it and applies log to the copy.

Please help