Hi @gcelec,
The DVL functionality is available in Companion 0.0.31 (it doesn’t require a git branch anymore - apologies that we apparently haven’t updated that documentation yet), which also includes a change that explicitly avoids sending data to the autopilot if the DVL is reporting it as invalid. Previously those values were sent through with a confidence of 0%, but the vehicle was consuming them anyway and using them as valid, which understandably isn’t very helpful. I would guess that change should at least stop the vehicle from running away in position hold (because it won’t let you engage position hold without a trusted position source).
For the missing parameters, ArduSub 4.1 is more recent than QGC 4.0.5, so QGC doesn’t know how to handle it properly, and it looks for old parameters that don’t exist in more recent ArduSub versions. QGC 4.1.4 should fix that, although QGC 4.2.0 was apparently released late December, so may be a better option to try first (because it’s more recent, so will have more bug fixes and some feature improvements).
On the compass spinning front, I’m not certain what the issue is there but in this comment it was mentioned that it seems isolated to QGC 4.0.5, so that may also be fixed by updating your QGC version.