Tentacles 0.5s out of sync immediately after jamming

Immediately after jamming two tentacles from my Sound Devices 633, I connected them each to my iPhone to verify the the timecode values. On each tentacle, the TC value was about 0.5 sec late out of sync with the master clock on the 633.

Ive never heard of this problem from post, but this is also the first time I check the TC values against the master clock.

Any idea what can cause this? App running on an iPhone 5c IOS 10.3.1.

Thanks!