Limit switch failures with Rambo 1.4

I recently picked up 10 limit switches from Mouser. They are the same make and model that Ryan sells. The photo is incorrect, they have the quick connect terminals.

System
Board: Rambo 1.4
Firmware: Marlin_V1CNC_Rambo_DualLR_2.0.7_506
Switches: Omron SS-3GL13PT

Issue
Unused switches show good continuity. Upon install, switches show “open” with M119 command. After homing (works correctly), switches appear to stick with further M119 commands showing the switches as “TRIGGERED” indefinitely. Upon removing the switches, the continuity test now fails.

Investigating
The endstop connections on the Rambo board are showing a constant 0.64mA at 4.95V. This appears to be well within the defined specifications for the switches. Switches show no obvious signs of damage. Connecting a jumper directly to the Rambo connections shows “open” as expected on M119.

Inquiry
Is it likely I got a bad batch of switches?
Has anyone experienced a similar issue?
Is there something I’m overlooking?

Other options
I have already ordered switches of another flavor to see if they will make a difference, but must wait for delivery. However, I’d like to determine whether I have a bigger problem before killing another batch.

Any insight is appreciated. Thanks!

How weird. I guess you got some one time switches? :slight_smile:

I would be taking one apart to see if there is any evidence on how they might have gotten stuck.

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I opened one up and couldn’t see anything obvious. By eye alone, the circuit looks complete, but it must not be. If I jiggle the copper tab around, I can get tone. It’s like something in the connection is not fully conductive. No evidence of corrosion.

Or maybe it’s one of those fancy EA pay-per-click models and I just need to refill my balance. :laughing:

Amazon seems to think they can get me some more switches today, so I’ll just give them a whirl.

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