Fix for Inconsistent Motor Response in Modkit

Hi All,

We have worked extensively with VEX to get to the bottom of an issue that affects motor execution in Modkit programs. Some of these issues and a workaround have been reported on this forum:…modkit-for-vex

The latest information and Motor Firmware fix is available at:…-temporary-fix

If you are experiencing any inconsistent motor behavior (motors not running as expected, inconsistent waits after drivetrain moves etc) we urge you to see if this fix helps you and to report any success (or failure) here. This fix will be rolled into an upcoming motor firmware release so any feedback we can get over the next month would be great.


I downloaded the fix last night and my motors are still inconsistent. Sometimes the robot will move correctly, but more times than not it will still not.

Modkit: Thank you for this post. Was just about to ask about other’s experience with motors waiting between moves. Right now, it’s our teams’ biggest issue with programming. We are a new team and have yet to compete in official tournaments. Before we do, I was hoping to fix these issues. There seem to be many “pauses” between moves and I was hoping to find solutions. We will try the fixes above. Is there any difference between the free version and the paid? We have been using the free version and are currently in the process of getting a school license.

Thank you ModKit.

NES: If you are still experiencing problems please ensure that you remove any “set timeouts” you have in your motor code. This was often used as a workaround and when set to a very small timeout this can end up causing more problems than not since the motors will timeout inadvertantly whenever they don’t move for a small amount of time.

If you are still experiencing issues after removing all your set timeouts, please make sure to send a technical support query to and reference this forum post. The issue is on the VEX firmware side side and was fixed to the best of our understanding but VEX will certainly want to know about cases where it is not fixed.

MGrobbel: The main difference is where you save - in the cloud for online and on the desktop for desktop. We recommend the desktop for schools because it eliminates the need to fumble with saving passwords. Also purchasing the software supports our development and helps us continue to improve it including investigating bugs which helped lead to this fix :slight_smile:

ipanavigator: You’re very welcome!


Hi. I am posting in reference to the issue of inconsistent motor response using Modkit. One of my VEX IQ teams is getting very frustrated with this issue, as they have code that works only some of the time and the state competition is a little over a week away. Below is the link to their code for their robot (tried uploading but it failed for some reason). They have set it up so that the touch sensors run each part of their program. The program had occasional issues but worked pretty consistently until we began expanding it to do even more, and now it works very inconsistently. We tried separating the code into different programs with only minimal success. Please help. Thanks!

This thread is old, but we seem to have this issue in 2019! We just started using modkit because RobotC was too hard to figure out.
Is there a new fix for mod kit??

Are you certain firmware has been updated for all parts?