I occasionally see this error in my console. (See attached screenshot.) I have not found a way to reliably reproduce it, but it seems a bit of defensive code on your end would clear it up. We are on 15.3.0.
Thanks.
Hi @dhaber
I do not see any similar reports on our Github issue board.
We can see that it comes from the mouseover hook while using nestedHeaders. Do you get it when you perform such an action? Any details regarding steps to replicate the issue and a demo would help us much as with no related reports and our nestedHeaders demo showing no errors there’s not much I can do to help.
Understood. Next time it happens I’ll spend more time to see if I can isolate what series of steps triggers it.
Thanks.
Hi @dhaber
Were you able to investigate the subject further?
Hi @aleksandra_budnik. I’ll take a look in the next day or two and get back to you.
Thanks.
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We are still seeing this exception hundreds of times a day in our New Relic monitoring. I have uploaded the stack trace as captured by New Relic. Please let me know if that gives you more to work on. Thanks.
Thank you for sharing screenshots, @dhaber
I tried to replicate it in the documentation, but wasn’t able to. Do you get this error on any demo of our documentation? Here is the link Column groups - React Data Grid | Handsontable
Perhaps it is also system/browser-related. I am on macOS 26 Chrome 142 (no scale/zoom applied).
If that is replicable only in your application, I would need to ask for a demo. You can also check if updating to v16.2.0 (latest version) changes the outcome. You can also post what features do you use along with nestedHeaders and I’ll try to replicate it in a sandbox.
Hi @aleksandra_budnik. These exceptions are coming from our monitoring of our live users using the deployed application in production. I don’t know the steps that cause it, so I have no way of reproducing it in your demos. All I know is that it’s happening a lot. 
With respect to other features we use, one that comes to mind that could be related is fixedColumnsLeft, as we use that quite often in our grids. (We are careful to never merge headers across that boundary.)
Hm.. that will be hard to fix 
do you maybe have any device/system related data? Maybe the issue relates to a certain device/os combination or speed of action or cspecificsteps?
We have tons of device/system related data. 
Of the 6,630 instances of this error in the last month:
- 100% of the time it is a desktop device.
- 59.3% of the time the user is in Chrome, 40.7% user is in Microsoft Edge.
- 96.4% of the time the OS is Windows, 3.6% user is on a Mac.
- 80.2% of the time userAgentVersion is 142, 18.1% it is 143, with the rest in slightly older versions.
Instances are spread across our worldwide users.
Instances are also spread across many of our Handsontable grids, so it’s not limited to a particular screen.
I was able to find a session trace, which seems to indicate some mouse event over the manual column resizer just prior to the error:
Does that help?
Thank you for sharing @dhaber, based on this analysis, I’m at 3.6% part with my macOS. I will ask our QA to check it out on Windows.
My guess is that the OS percentages are based on our user base and not based on the likelihood of an error. More importantly, did the mouse interaction over div.manualColumnResizer help? It looks like your demo grid does not have manualColumnResize set to true, so you should try to reproduce the problem with that set (as well as fixedColumnsLeft, as I suggested earlier).
I tried that Handsontable example - JSFiddle - Code Playground
I used
- nestedHeaders
- fixed columns on the left side
- manual column resize
- with and without row headers
on that Chrome 142/macOS 26.0 (no zoom/scale) and did
- resize one column
- select multiple columns and resize them
- double resize a header one by once and expand it
- scroll the table and work shink/expand the fixed column
using the latest version of Handsontable - 16.2.0 (vanilla version).
I also checked some old posts you reported where you mentioned that you use mergeCells but that was also checked here Handsontable example - JSFiddle - Code Playground (no errors).
Maybe we can move to emails and schedule a code review?
I got feedback from our QA and he was not able to replicate the issue. We have the line of code that produces the issue handsontable/handsontable/src/plugins/nestedHeaders/nestedHeaders.js at develop · handsontable/handsontable · GitHub , and it possibly connects to the execution of this.hot.getSelectedRangeActive(); but without a demo to replicate the issue we can only guess what is wrong.
Hi @dhaber
is there a way we can move this topic further?
I would love to, but until I can reproduce it on demand, not sure we can.
I am now running 16.2.0 locally. Next time it happens I will try to see if I can reproduce it. If I can I will reach out.
Thank you for the update. I hope we’ll be able to work it out soon, till then, happy 2026!
And the same to you @aleksandra_budnik! May it be a very successful one for you (and thereby for us)!
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