I run gkrellm from the init file of my window manager (fvwm) with:

  gkrellm -geometry +0-0

(i.e. at the bottom left).

The problem is that the window sometimes appears partly off-screen.
I can't reproduce the problem when running this command manually.

What seems to happen is that the window appears with an initial size,
then its height is increased. It is usually increased toward the top,
which is fine, but it is sometimes increased toward the bottom.

I've attached my .gkrellm2/user-config file.

With 2.3.11-1, I could reproduce the issue when running this command
manually.

I'm wondering whether this is caused by bug 900091 (or perhaps just
related), which I had reported in 2018. Here I got:

[fvwm][GetWindowSizeHints]: <<WARNING>> The application window (id 0x5600003)
  "gkrellm" has broken size hints (inconsistent with current size).
    fvwm is ignoring those hints.    hint override = 0, flags = 230
  min_width = 156, min_height = 651, max_width = 156, max_height = 651
  width_inc = 0, height_inc = 0
  min_aspect = 0/0, max_aspect = 0/0
  base_width = 0, base_height = 0
  win_gravity = 1
    If you are having a problem with the application, send a bug report
    with this message included to the application owner.
    There is no need to notify fvwm-workers@fvwm.org.