@girish Increasing the swap seems to have cured the problem. Additionally, there may have been a problem caused by a misreading of the amount of swap as originally on the Linode it said there was only 512mb but in Cloudron it said there was almost 1GB.

I have increased the swap from 512mb to 2048mb and I haven't received any app out of memory notifications since then so that seems to have cured it.

Thank you for your help.