This evening my blinds did not automatically close, so I jumped on my HA box expecting to see a reboot or crash, but HA was running just fine. So I manually clicked “Run” on my automation to close the blinds, and that didn’t work. After some more digging I realized that set_position(int) doesn’t seem to be working anymore, however close and open operations do. I use set_position to lower my blinds to 50% during the afternoon.
Did something change here on the SmartThings API?
I would look at your blinds themselves on the SmartThings side. They’re undergoing quite a change as they move away from the Groovy infrastructure.
Did the blinds transition to an edge driver? If so which one? What does that driver expose to the system and therefore to HA?
I’m going to need you to talk to me like I’m a 3rd grader 
So the blinds I added to my SmartThings hub just as a “generic z-wave device” because they are some random manufacturer. So nothing changed on the blinds for sure. I’ve also not upgraded anything on the hub itself. So the only thing I can think has changed is the SmartThings cloud API.
I don’t know enough about how HA integrations work under the hood (or even, frankly, where that code lives so I could take a look) for me to see how the integration is translating the cover.set_cover_position to a SmartThings cloud API call.
I presume if that cloud API call was accepted by SmartThings, and it reached back into the hub, it would be processed by the blinds correctly given that nothing has changed here locally. Which is why I’m thinking that cloud API call simply no longer exists or has been modified.
Not exactly…
Ok. SmartThings devices are all governed by:
Prior to January and some legacy devices that have not been migrated yet. Device type handlers. (DTHs) using the Groovy infrastructure.
All of that is going away in favor of the new infrastructure using LUA - its called EDGE. All ZWave and Zigbee devices on smartthings use these DTHs or drivers.
If you do NOTHING SmartThings is very much hard at work right now automatically changing user DTHs for Edge drivers.
This is usually transparent to the user but it’s not been without problems.
Because HA does NOT talk to your smartthings devices directly - and only send instructions to the st cloud which interprets the command and then use the DTH or driver to communicate with the device… These are INTEGRAL to how ST works (and part of why I dislike thier infrastructure)
They’re changing stuff under the hood without your intervention right now at a fundamental level.
Now. Knowing that. Where is the most likely issue?
Seems to be related to Edge drivers as I’ve just posted on the same issue: