Set Participant Data action overwriting previous variables in Architect flow

Running into a weird behavior with the Set Participant Data action in Architect. I’m trying to pass a few custom variables from an IVR menu into the queue context so the agent sees them on the screen. I have a JSON payload being built via a previous data action, looks like this:

{
 "custom": {
 "product_type": "insurance",
 "priority_flag": "high"
 }
}

When I hit the Set Participant Data action, I map the product_type key. The variable shows up fine in the debug logs. But when I try to add a second Set Participant Data action further down the flow to set priority_flag, the first variable disappears. It seems like the action replaces the entire custom object instead of merging it. I’ve checked the docs but nothing mentions merge behavior. Is there a specific syntax I’m missing to append to the existing participant data without blowing away what was already set? The flow ID is a1b2c3d4-5678-90ab-cdef-1234567890ab if that helps.

Tried using the same action with multiple keys but the UI only accepts one key-value pair at a time. Feels like a bug but might be user error. Anyone else hit this wall?