Variable CPI printer file

About the middle of May, a report program that has been
running some years was creating the a spool file using:

Page size:
Length . . . . . . . . . . . . . . . : 68
Width . . . . . . . . . . . . . . . : 198
Measurement method . . . . . . . . . : *ROWCOL
Lines per inch . . . . . . . . . . . . : 8
Characters per inch . . . . . . . . . : 20

These spool files print as expected creating a tightly spaced
but readable report.

Sometime after that something changed and a re-compile
using the same parameters produces a slightly different spooled
that is different in this one very important respect:
Device requirements:
. . .
Variable CPI . . . . . . . . . . . . : Y
. . .

The printed result is an almost unreadable mess with heading data
on the right truncated and detail lines wrapping. The horizontal
spacing seems something like an extra 30%

Older spool files print as expected, but any report created from the
newly-compiled spool file have this terrible problem.

Any advice regarding how to avoid the Variable CPI very much appreciated !