Dual monitors in Bookworm

Having an odd spot of trouble with Bookworm and dual monitors.

The initial setup consisted of a pi5 with a single HDMI monitor
on HDMI0 (next to power connector).  Worked fine, no problems.

Then I connected a much older DVI monitor with an adapter to
HDMI1. After a couple of retrys, it too was recognized and the
Screen Configuration program allowed me to position the monitors
as desired. Menu bar stayed on the HDMI monitor, with the DVI
monitor supplying extra desktop space.

After a few reboots, the reproducible behavior is to have the
early boot messages show up on both monitors. After some output
related to disk discovery only the DVI (so, HDMI1) monitor gets
the rest of the boot output while the monitor on HDMI0 goes to
sleep. It never wakes up. HDMI1 becomes the sole monitor, with
the menu bar across the top. Screen Configuration does not see
the second monitor.

I suspect this has something to do with the monitor on HDMI0,
a Dell ST2220L, having a very quick power save timer. It goes
to sleep in about six seconds.

Anybody have a hint how to work around this behavior? Ideally,
I'd like to keep the Dell ST2220L as the primary monitor, with
the menu bar at the top. The DVI monitor, a Dell 2405FPW, uses
much more power (~60 W) and will be turned on only when extra
screen space is needed.

Thanks for reading, and any ideas!

bob prohaska