Notifications stop sending

[jjslegacy]

Having an issue with notifications - email and send to Smartthings. After a while they stop sending and I see messages like this in the logs with the numbers climbing.

I am guessing ST stops responding and the notification never cancels out and so it just gets stuck adding on and after the first stops the rest get queued?

2020-07-08 18:31:38,376 INFO: Background notification functions running 1717. [in /opt/alarmdecoder-webapp/ad2web/notifications/types.py:438]
2020-07-08 18:31:43,491 INFO: Background notification functions running 1717. [in /opt/alarmdecoder-webapp/ad2web/notifications/types.py:438]
2020-07-08 18:31:48,538 INFO: Background notification functions running 1717. [in /opt/alarmdecoder-webapp/ad2web/notifications/types.py:438]
2020-07-08 18:31:53,585 INFO: Background notification functions running 1717. [in /opt/alarmdecoder-webapp/ad2web/notifications/types.py:438]