Hello,
I was in the process of upgrading the Bryntum Grid library to 5.5.3 to support our Lightning Web Components and during testing I noticed a problem with the combo filterable column configuration. Whenever I make a selection of a filter option in the dropdown, the grid correctly filters down the data, but the input cannot be dismissed and when clicking the X to clear the input, a component error is thrown. I was not able to reproduce this on your online example so I'm curious if this is specific to Lightning Web Components. Would you be able to confirm whether this is reproducible on your end? This was also reproducible in 5.5.2. We were previously using 5.3.5, which does not have this issue.
Attached is a recording of the encountered issue and also a screenshot of the browser console error output.
Let me know if you need any additional information. Thank you.