# Modbus behaving inconsistent on 5.21.0

**URL:** <https://forum.universal-robots.com/t/modbus-behaving-inconsistent-on-5-21-0/38578>\
**Category:** Report a Bug\
**Created:** [February 14, 2025, 1:42pm UTC](https://forum.universal-robots.com/t/modbus-behaving-inconsistent-on-5-21-0/38578 "2025-02-14T13:42:38Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![nh11](https://avatars.discourse-cdn.com/v4/letter/n/df788c/32.png) [@nh11](https://forum.universal-robots.com/u/nh11)\
**Post date:** [February 14, 2025, 1:42pm UTC](https://forum.universal-robots.com/t/modbus-behaving-inconsistent-on-5-21-0/38578/1 "2025-02-14T13:42:38Z")

</div>

Behavior:  
We had customers report that our Gas test and other secondary interface buttons behaved inconsistently. This secondary interface is a simple modbus signal call.

Workaround Suggestion:  
Downgrade to earlier version, specifically 5.17.3. This worked

Affected Version(s):  
5.21.0