Minecraft PE needs to restart before connecting

I’ve set up a Minecraft Bedrock server, which works great. I can connect from Minecraft on Windows 10. However, whenever I try to connect from Minecraft PE on iPhone or iPad using an app I had running in the background, it can’t find the server, I just get the wavy line on Current Ping. I have to explicitly kill the iPhone/iPad app, start it again, go back to Servers, and it sees it straight away. So this doesn’t seem to be a server issue, it looks to be a bug with PE. Has anyone else seen this and know of a solution, aside from keep restarting the app every time before joining?