Typical Problem , There are 4 germanium diodes in between the input and
output connectors on a small board. 2 of them are voltage dividers and 2
of them are for forward / reflected power . Most likely "1" of those
germanium diodes is open , this would give you exact 1/2 reading.

Chris wrote:

I have a Dosy PM-1000-TS meter that isn't reading peak or PEP anywhere near
correct. It reads less than half of what it should. Does anyone have or know
where I can find a schematic for it? Any ideas what might be bad?

Thanks,
Chris