SageTV crashes on shutdown when using PrePlugin filter (Windows)

When a PrePlugin Filter is configured (in this case [DVDBDecrypter](https://forums.sagetv.com/forums/showthread.php?p=549074)), shutting down SageTV I don't get a graceful shutdown but it crashes out in the Graph teardown of the first tuner at GraphManager.cpp#L446
SAFE_RELEASE(pCapInfo->pPrePlugin);

This doesn't occur in SageTV V7, but does in SageTV V9
Without a PrePlugin filter configured, SageTV V9 shuts down correctly

Using GraphEdt the filter does load and unload successfully

While looking into this, VS2015 was producing numerous warnings about
signed/unsigned mismatch
conversions between data types and possible data loss
So thought I'd deal with those first, but need to try and get to the bottom of this issue

John