[Heathkit] SB-610 CRT Trace Question

[Carl Lowry]

I'm redoing a couple SB-610s.
Have thus far replaced "all" electrolytic caps, as well as "all" other caps, 
and the resistors hanging off the Intensity & Focus pots.
I went back to 2002 here on the Forum & researched all i could find.
Have also replaced "all" tubes except the CRT.
Now i have a real sharp & excellant trace on the CRT scope.
Question though:
When i first TURN ON the SB-610 as well as when I go from TRAP or RTTY back to SINE the trace "wanders around" (horizonal wise).
It goes from the right hand side of the CRT  ...... stretches out to a "real good & sharp"  trace line & then after a few seconds
adjusts back & centers itself within the grid patterns.
Is there a perhaps voltage problem or is this a common thing on all SB-610s ?
Thanks for your advice.
73s
Carl , k4zrd