Why bonita transform my STRING into BIGINT ?

I created a buiseness data : PROGRAMMEUR and I declared TIMEZONE as a STRING (not a BIGINT !!). Why have I this error when I submit my form ??

Caused by: org.h2.jdbc.JdbcSQLException: Data conversion error converting "'PARIS' (PROGRAMMEUR: TIMEZONE BIGINT NOT NULL)"; SQL statement:
insert into PROGRAMMEUR (persistenceId, ALLDAYEVENT, ENDEDDATE, ID, STARTEDDATE, TASK, TIMEZONE, ESTAPPROUVEE, persistenceVersion) values (null, ?, ?, ?, ?, ?, ?, ?, ?) -- (NULL, ?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8) [22018-175]