# Very odd bug? Unexpected failure and resolution to parameter resolution in UDTs

**URL:** <https://forum.inductiveautomation.com/t/very-odd-bug-unexpected-failure-and-resolution-to-parameter-resolution-in-udts/115017>\
**Category:** Ignition\
**Tags:** ignition83\
**Created:** [April 11, 2026, 12:16am UTC](https://forum.inductiveautomation.com/t/very-odd-bug-unexpected-failure-and-resolution-to-parameter-resolution-in-udts/115017 "2026-04-11T00:16:21Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![bryan.boone](https://avatars.discourse-cdn.com/v4/letter/b/ba8739/32.png) [@bryan.boone](https://forum.inductiveautomation.com/u/bryan.boone)\
**Post date:** [April 11, 2026, 12:16am UTC](https://forum.inductiveautomation.com/t/very-odd-bug-unexpected-failure-and-resolution-to-parameter-resolution-in-udts/115017/1 "2026-04-11T00:16:21Z")

</div>

Maybe I’m missing something, but my UDT has fields (for “raw” tags) like:

```python
        {
          "name": "Temperature_Raw",
          "tagType": "AtomicTag",
          "valueSource": "opc",
          "opcItemPath": "[{DeviceName}]HR49",
          "dataType": "Int2",
          "readOnly": true,
          "engUnit": "",
          "opcServer": "{OpcServer}"
        }

```

with the parameters OpcServer and DeviceName, but when I create an instance from this UDT and fill in these parameters nothing resolves:

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/f/9/f9d845e606ef61f58d2ffc6182695fb5812bdb32.png)

But when I inspect the (raw, actually read) tags and do nothing but select “override” on BOTH tags:

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/6/6/66f23f6a5b0ede99e3fe6e95a81b90c022b51018.png)  
Suddenly it resolves, and resolves correctly…. but why? What’s causing the pause and re-evaluation? Is there a button to do “this” re-evaluation everywhere at once?

---

<div class="post-metadata">

**Author:** ![bryan.boone](https://avatars.discourse-cdn.com/v4/letter/b/ba8739/32.png) [@bryan.boone](https://forum.inductiveautomation.com/u/bryan.boone)\
**Post date:** [April 11, 2026, 12:29am UTC](https://forum.inductiveautomation.com/t/very-odd-bug-unexpected-failure-and-resolution-to-parameter-resolution-in-udts/115017/2 "2026-04-11T00:29:03Z")

</div>

Ah. I’m missing the binding members entirely. My fault for being so lazy.

> ```
> "opcItemPath": {
> "bindType": "parameter",
> "binding": "\[{device}\]HR49"
> },
> "opcServer": {
> "bindType": "parameter",
> "binding": "{opcServer}"
> },
> 
> ```