@gael could share more details regarding which openmrs version you are using
Also hope you have remove/disabled the old fhir module
The version I use of the platform is 2.3.2 and the reference version is 2.11
Which version of the FHIR2 module are you using?
the module that has the reference application is fhir2 1.1.0 remove the module and openmrs worked correctly