Prior to Koha version, 18.05.10, if a library has the CIRCAUTOCOMPL system preference set to TRY, Koha would attempt to search for the patrons name during checkout (circulation.pl) or when placing holds for a patron (reserves.pl).
In Koha 18.05.10, Koha is still attempting to complete the patron's name when using the checkout feature, but not when placing holds for patrons. The spinning thing does not appear when starting to type the patrons name on the reserves.pl page but does continue to work in the circulation.pl page.
this was a result of a Rmain mistake in 18.05.x
commit daac05e506efdb6038dd9978aa3f55911c97bf3a fixes it and is backported to 18.05.x for 18.05.11