Manually add new registrant through the front end

Our event season has just started and we have come across an issue while trying to add registrations through the front end.
We are able to create new entries through the admin interface and members directly are able register themselves.
If the initial user record is created in the back end it is then possible to edit it and save the record in the front end.
When trying to create a new record on the front end if the user search option is clicked, in the form that opens up it is not possible to search for a member correctly as typing part of the user name and pressing the search icon results in the window closing and "Null" appearing in the user field.
If the user search option is clicked and the required entry is found and selected by scrolling down the records the required details are then automatically added as expected. When trying to save this new record however an error is reported "Unsupported operand types: float + string"

Is this a permissions issue or a joomla 4 specific issue?

Joomla version 4.0.5
Events Booking 3.17.6

I have just tried from the front end again while using an account with "super User" group access. The search behavior is the same and on saving the same error is reported of: Error 0 "Unsupported operand types: float + string"

Hello Mike

That's strange to me. For this, could you please submit a support ticket sending us super admin account and link to the page which we can add registrants and see this error.

We will check to see why the issue happens and get it sorted

Regards,

Tuan