This drivs me crazy, near every damn time So this is an incomplete
experiment to start to trace what the problem is maybe its cos uname
-r on ctm delta generator server (a jail so not in my complete
control) keeps upgrading, & my client receipient is older ?

cd /pub/FreeBSD/development/FreeBSD-SVN/tmp 
ctm -q /pub/FreeBSD/development/CTM/svn-cur/svn-cur.1[0-9][0-9][0-9][0-9].xz
Release number mismatch: found 371524, need 371527
/pub/FreeBSD/development/CTM/svn-cur/svn-cur.10002.xz Fatal error: Assert failed.

*** old/ports/misc/ctm/files/patch-ctm_ctm__pass2.c 	Thu Mar 24 10:41:29 2022
--- new-jhs/ports/misc/ctm/files/patch-ctm_ctm__pass2.c	Mon Apr 18 17:35:02 2022
***************
*** 66,73 ****
  +		    if(Verbose > 3)
  +			printf("Actual release number %d\n",rel2);
  +		    if (rel != rel2) {
! +			fprintf(stderr,"Release number mismatch: found %d, need %jd\n",rel2,rel);
! +			WRONG
  +		    }
  +		    break;
  +		case CTM_F_Forward:
--- 66,73 ----
  +		    if(Verbose > 3)
  +			printf("Actual release number %d\n",rel2);
  +		    if (rel != rel2) {
! +			fprintf(stderr,"WARNING Release number mismatch: found %d, need %jd\n",rel2,rel);
! +			WRONG // hashing this out still sees it exiting after each single delta
  +		    }
  +		    break;
  +		case CTM_F_Forward: