Per my other thread, I’m having this exact issue. Here are my answers.
UPDATE: Ok, weird. I can now add my instance. I didn’t change anything.
Approximately how many devices are on your ST account?
Approximately how many devices are associated with webCoRE?
315-330, I can’t access the webCoRE instance so I had to count in the mobile app.
Can you remove devices from webCoRE that are not used in your pistons via the webCoRE smart app or does the app also produce errors?
I can only remove 6 that are not being used. I removed them, no change.
Did you add or remove any devices around the time this problem began?
I have been adding a lot of devices. I added about 10 zigbee motion/contact sensors and about 8 z-wave switches/dimmers. I have about 20-30 more devices to add.
Have you noticed any specific devices not working, missing, or otherwise acting up in SmartThings?
YES! - Since adding the 18 devices noted above, I started experiencing a lot of issues with webCoRE triggering correctly and saying it sent the command to the device but the device not responding. Then a few minutes later I would trigger the same piston/automation and it would work. I tried repairing both the z-wave and zigbee meshes. I can’t say that it improved any.
I have about 10 webCoRE instances. I have been having lots of performance issues with webCoRE. I suspected due to the number of devices I have. Some instances have always been split out due to wanting to separate security, leak, fire automatons so I don’t break them on accident. I’ve also split out my notifications handling as I have been working on something similar to you for custom/intelligent messaging. I have a “Presence” instance that handles my more complicated presence logic that doesn’t need to be in my main instance. My main instance handles 80% of all of my automatons. It would not be easy to split out. I can say that I have likely only added a few pistons to that main instance (which is the one I cannot access).