occasionally a completely erroneous PARAMETER a=b statement is emitted with no diagnostic and no obvious cause

[weatherhead99]

I am finding random illegal PARAMETER sequences emitting, e.g.

PARAMETER29="IF SciStart SciStart=0"
PARAMETER30="IF !summit_sci_is_integrating summit_sci_is_integrating=0"
PARAMETER31="IF FcsStart FcsStart=0"
PARAMETER32="IF summit_sci_is_integrating summit_sci_is_integrating=0"
PARAMETER33="IF SciStop SciStop=0"

in the .acf file. These are not only illegal constructs for a PARAMETER= line, but also would be illegal in a sequence file.
This code does not appear anywhere in the input, and I as yet have not been able to find a way to prevent it being emitted.