I assume that the registrar is rewriting the request URI of the request to the SIPS scheme. The behaviour of the registrar by adding a SIPS also to its Record-Route header is then according to the standard:
``` The URI placed in the Record-Route header field MUST resolve to the element inserting it (or a suitable stand-in) when the server location procedures of [4] are applied to it, so that subsequent requests reach the same SIP element. If the Request-URI contains a SIPS URI, or the topmost Route header field value (after the post processing of bullet 6) contains a SIPS URI, the URI placed into the Record-Route header field MUST be a SIPS URI. ```
You could set the rr parameter "ignore_sips" on the registrar, if you want them to only insert the SIP scheme.