We just released particles package version 2 recently with Uikit3 framework and re-build all particles structure(new features, improvement and bug fixes). At the moment, I recommend you use the particles package which included for the theme/template.
If you build a new site, you can use our new particles version2 package.
Did you implement any new particle recently https://joomlead.com/gantry-5-particles/ that came with the uikit3 js/css file?
NOTE: We will include both particle package (version 1 and 2) in the next few days.
Back to the issue: I guess its a conflict between uikit version 2 and 3. Could you please submit a private ticket to our ticket system https://joomlead.com/ticket-support/ so We can help you check it?