Nextdns Android play store app keeps stopping.

On two different  Samsung android phones, the nextdns play store app keeps intermittently closing all the time and does not provide any error messages that I am aware of.

This happens regularly, the app will not run for more than a day or two before stopping. I am therefore using the device without secure dns until I realise the app isn't running. 

I have also removed the app from android battery optimisation, just in case that 2as the case but that has made no difference 

Is there a way of making this more reliable  so it runs consistently, or is there another more reliable way of setting up DoH?

I have already tried the android private dns setting, but this uses DoT and gets blocked by some of the networks I connect to, so not ideal having to disable and re-enable all the time. 

Thanks.