Hmm, I can’t seem to find a reason why this is happening. Admittedly, I’m not too familiar with using the dropdown interaction. I found this discussion and it appears that you’ve followed all of the steps. Might be a conflict with your sub-dropdowns since the interaction targets the list element.
Have you considered creating a custom dropdown for those sub-dropdowns? Meaning, not using Webflow’s native dropdown element? This could help. The downside is that when clicking a second sub-dropdown, the others will not close automatically without the use of some additional code.