reintegrate merge failing because "can only be used if revisions <snip> were previously merged", but it's a lie (I think?)

Howdy,

        I have a trunk and a feature branch. Time has come (it was long, over a year) to reintegrate back into trunk. I have subversion 1.8 on both server and client (though a year ago, we were using 1.6 server and client).

        I have recently (like yesterday) merged trunk to branch successfully. It passes verification and sanity testing. I like the branch.

        From within an up-to-date trunk working copy, if I attempt the merge branch back to trunk I get some complaints:
[charletr_at_ariesbld trunk]$ svn merge ^/6WINDGate/branches/DUAL_SSL_Inspection . --dry-run --accept postpone
svn: E195016: Reintegrate can only be used if revisions 15725 through 26003 were previously merged from https://csvnrose-pro.rose.hp.com:18180/svn/tpt-6wind/6WINDGate/trunk to the reintegrate source, but this is not the case:
  6WINDGate/branches/DUAL_SSL_Inspection/ports/lsm/lsmclient/test/cukes/features/1_package_update
    Missing ranges: /6WINDGate/trunk/ports/lsm/lsmclient/test/cukes/features/1_package_update:19595
  6WINDGate/branches/DUAL_SSL_Inspection/ports/xtrap/scripts
    Missing ranges: /6WINDGate/trunk/ports/xtrap/scripts:21872
  6WINDGate/branches/DUAL_SSL_Inspection/user/switch/sdk-xgs-robo-6.4.0/systems/linux/kernel/constellation-2_6
    Missing ranges: /6WINDGate/trunk/user/switch/sdk-xgs-robo-6.4.0/systems/linux/kernel/constellation-2_6:17549,18282
  6WINDGate/branches/DUAL_SSL_Inspection/user/switch/sdk-xgs-robo-6.4.0/systems/linux/user/constellation-2_6
    Missing ranges: /6WINDGate/trunk/user/switch/sdk-xgs-robo-6.4.0/systems/linux/user/constellation-2_6:17549

[charletr_at_ariesbld trunk]$

        Soo... that's a bit hard to believe because I did just recently merge trunk to branch. Furthermore, if I go into my branch working copy and attempt to merge an exact change (let me pick revision 19595 as an example because it's first in the listing above), nothing happens:
[charletr_at_ariesbld DUAL_SSL_Inspection]$ svn merge ^/6WINDGate/trunk . --accept postpone -r 19595:19595
[charletr_at_ariesbld DUAL_SSL_Inspection]$ svn merge ^/6WINDGate/trunk . --accept postpone -r 19594:19596
--- Recording mergeinfo for merge of r19595 through r19596 into '.':
 U .
[charletr_at_ariesbld DUAL_SSL_Inspection]$ svn stat -q
[charletr_at_ariesbld DUAL_SSL_Inspection]$ svn ci
[charletr_at_ariesbld DUAL_SSL_Inspection]$

        FYI, here is the view of mergeinfo from my trunk and branch:
[charletr_at_ariesbld trunk]$ svn propget svn:mergeinfo ports/lsm/lsmclient/test/cukes/features/1_package_update
[charletr_at_ariesbld trunk]$

[charletr_at_ariesbld DUAL_SSL_Inspection]$ svn propget svn:mergeinfo ports/lsm/lsmclient/test/cukes/features/1_package_update
/6WINDGate/branches/zorro_trunk_merge/ports/lsm/lsmclient/test/cukes/features/1_package_update:21398-23471
/6WINDGate/production/aries_1.1.1/ports/lsm/lsmclient/test/cukes/features/1_package_update:21842,21867,21906,22087,22270,22334
/6WINDGate/trunk/ports/lsm/lsmclient/test/cukes/features/1_package_update:15746-19001,19597-25912
[charletr_at_ariesbld DUAL_SSL_Inspection]$

        Notice that 19595 is, infact, missing from branch's mergeinfo.

        In summary, A recent merge from trunk to branch suceeded, trunk cannot reintegrate because it claims that some change sets are not merged to branch, attempts to merge those exact change sets into branch produce a no-op, mergeinfo on branch confirms those change sets are missing.

        I'm stuck... any ideas what to try next?

--
Ricky Charlet
Software Dev / Routing Dude: Aries team, Roseville CA
ricky.charlet_at_hp.com
USA: 916.785.2090