Please excuse me for the delayed reply.
Instead of fixed delays, we typically recommend Waits and setting Ample Timeouts in your test so the steps stay in sync with the app. As far as I can see you've already tried waits and it didn't help. Please review the article about Ample Timeouts and give it a try. I also would like to test this directly, is there any way you can provide access to the website you are testing. Please note that you are currently writing in forum post and you should submit a ticket if you are going to post sensitive information since in the ticket all the info remains private.
Please also note that in some cases the only option for a running test is the use of fixed delays.
Looking forward to hear from you.
All the best,
the Telerik team