Issues when taking a booking backoffice admin for in person booking for a known existing customer.

Issues when taking a booking backoffice admin for in person booking for a known existing customer.

We are having some problems, with back office bookings.
When existing customers return in person to book, we cannot find them, MOST of the time.
We search in CRM & Bookings database. Even when the dropdown list shows a name, it says it cannot find them?
We have this issue with either CRM or BOOKINGS contact list, and are resorting to a default workaround by just adding a default customer as "Walkin" ?
In this example, it shows th eprogression when making a back office booking. I searched for the first customer shown, in the list, This is not the case usually but it shows the error?
I then typed the exacy full name, and even thought it was on the list shown, it returns £Search Results NOT found"
This is frustrating! Please help us,