While adding new authority record, several accents (such as é, è) are not stored properly. The record will get altered by the system. For example: Adding author "Velden, Thérèse" will end up as "Velden, Thers̈e"
Are you copying the strings from somewhere else? What's the exact version of Koha you are using? Please also provide the exact steps to recreate.
Sounds like a local (configuration) problem. SQL settings? Can insert these accents without problem in authorities.
Entered them via ascii code (alt+130, etc). But the problem seems to have fixed itself. Now able to enter these accents without any weird results again.
It could also be a problem if the LDR is missing (misconfigured frameworks) as the leader includes the information about encoding. I have seen similar problems with broken leaders for bibliographic records.