Here's some information that may be relevant to some people.
I've been trying to get the Tascam DR100mkii to lock to my Sound Devices 702 and also to a Forssell MADC-2 converter with no digital lock beyond 44.1k.
I called Tascam and they were not much help either (They said the tascam locks correctly with a number of outboard recorders they have in their shop and they said I should take it up with the manufacturers of my other outboard gear).
I then went deeper into the settings of the SD 702 and found a couple settings that allowed me to lock digitally at 96k
1- I changed the Digital Output mode on the SD702 from Professional to Consumer, then
2- I changed the Frequency from 96k to 96.096 in the SD702 and that allowed me to lock digitally to the Tascam with the 702.
Sooo, it seems the Tascam is clocked at 96.096 instead of plain 96K
Unfortunatelly the Forssell doesn't have those (varying frequency) options so in a sense the Tascam is useless to me as a bitbucket.
Peace
Marco Granados