This happens to me all the time too, basically because I don't wait for the charge to actually hit before swtching to zeal. So I get frozen quite often.
My solution is to get better at the timing for switching (wait til you hear the *slap* and don't keep your finger pressed at charge unless you intend to go on a series of knockbacks). When I get it wrong, I have a good rare shield and bstar on my switch so that I can actually finish the first zeal before coming back to weapon/shield set #1.
Quite scary to get frozen in HCL hell.
