Hotel Wake-up Calls - cannot create wakeup calls

Following the upgrade to FreePBX version 16.0.10.43, the Wake-up calls (version 16.0.1) module is not working properly. I am able to create wake-up calls through the phone, however when I try to create them through the web interface, I get the following error.

I've looked at the file, and line 882 contains the following:

Additionally, when I create a wake-up call through the phone, it seems to be successful (although the call hangs up after the voice says "wake-up call at") however, when the time comes for the call, the phone doesn't ring and I get the following message in the logs

Any indication as to why this is happening. I've tried re-installing the module and that seems to make wake-up calls made through the phone work, but it breaks any time I try and interact with the web GUI.

Thanks,

James