How to get out diagnostics at a frequency longer than the resubmission frequency

[Adrian-Lock]

I'm running an idealised LFRic simulation that I want to produce 3D instantaneous diagnostics every 12 hours. Until now I've been running in "crun" chunks of 1 day and this has worked fine - I get a diagnostics file every day with two times in it. I've now started running higher resolution and so can only afford to run in 6 hour crun chunks and sadly am not getting any 3d diagnostics at all. My guess is that the xios statement I'm using:

<file id="lfric_idl_3ddiags" name="lfric_idl_3ddiags" output_freq="12h" convention="UGRID" enabled=".TRUE.">
<field_group operation="instant" freq_op="12h" prec="4">

must be telling it to output diagnostics every 12 hours within each crun chunk, rather than in overall simulation time (and so my 6 hour chunks are never long enough)? Might that be correct? If so, how to I tell it to do the former (and produce diagnostics every 12 hours)?