Failed to gain semaphore lock

I was trying out UpdraftPlus to extract the our site in a format that our SEO consultant could work with, but it immediately fails with the following error message:

Failed to gain semaphore lock (fd) – another backup of this type is apparently already active – aborting (if this is wrong – i.e. if the other backup crashed without removing the lock, then another can be started after 3 minutes)

Enabling Debug mode, the detailed log shows lower level errors with the locking mechanism (whatever it is). Attempting to search the forum for the word “lock” returns nothing but “loading…”, which may mean no one previously seeing this or something wrong with the www.ads-software.com using banned URLs without clear error messages.

After going deep into the db plugin used (wp-db-abstraction), I found that it didn’t handle two of the SQL commands from the updraft-semaphore class correctly and added extra SQL dialog translation rules. Then the backup proceeded a lot further.

Anyway, here are the log messages before the fix (running on an old offline server, so don’t bother trying remote attacks):

0000.000 (0) Opened log file at time: Thu, 04 Feb 2021 19:51:20 +0000 on https://staging.i.wisemo.com
0000.016 (0) UpdraftPlus WordPress backup plugin (https://updraftplus.com): 1.16.47 WP: 4.9.8 PHP: 7.2.5 (cgi-fcgi, Windows NT STAGING 6.1 build 7601 (Windows Server 2008 R2 Enterprise Edition Service Pack 1) AMD64) MySQL: Microsoft SQL Server 2008 R2 (SP3) – 10.50.6000.34 (X64)
Aug 19 2014 12:21:34
Copyright (c) Microsoft Corporation
Express Edition with Advanced Services (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1) (Hypervisor)
WPLANG: en_US Server: Microsoft-IIS/7.5 safe_mode: 0 max_execution_time: 900 memory_limit: 256M (used: 26.8M | 2M) multisite: N openssl: OpenSSL 1.1.0h 27 Mar 2018 mcrypt: N LANG: ZipArchive::addFile: Y
0000.016 (0) Free space on disk containing Updraft’s temporary directory: 49110 MB
0000.031 (0) Tasks: Backup files: 1 (schedule: manual) Backup DB: 1 (schedule: manual)
0000.031 (0) Semaphore (fd, wp_options) in an impossible/broken state – fixing (1)
0000.062 (0) Requesting semaphore lock (fd) (apparently not via scheduler)
0000.062 (0) Semaphore lock (fd, wp_options) failed (line 43)
0000.062 (0) Failed to gain semaphore lock (fd) – another backup of this type is apparently already active – aborting (if this is wrong – i.e. if the other backup crashed without removing the lock, then another can be started after 3 minutes)