I had something similar where the computer would sleep and then immediately wake up again. It was my wireless mouse constantly sending a signal.
I solved it with this systemd service:
[Unit]
Description=Disable USB Mouse wakeup triggers
[Service]
Type=oneshot
ExecStart=/bin/sh -c "echo XHC0 > /proc/acpi/wakeup"
ExecStop=/bin/sh -c "echo XHC0 > /proc/acpi/wakeup"
RemainAfterExit=yes
[Install]
WantedBy=multi-user.target