strange behaviour on open – menu painted in two steps

Hi,

I’ve an issue with that menu. I use about 7 top level menu entries and about 15 more located as submenus. Whenever I click on one of the menu entries to open a page, the page opens but the menu on the new page gets “repainted” in two steps: 1. the menu appears as a long list, containig 22 menu entries in one large row. Then it takes about half a second and the menu then is shown formatted correctly. Only the 7 top level entries are shown as expected. I also tried the jQuery Vertical Accordion Menu but it bahaves the same way. Also in a quite fresh wp installation. Does anyone knows what might be wrong ? After a few more tests I figured out it works better after deactivating some time consuming plugins. Is it possible that if the page gets to slow (for whatever reason) the menu gets “painted” in two steps ?

thanks for your help!
Thorsten

https://www.ads-software.com/plugins/jquery-vertical-mega-menu/