Sounds like damp wood to me, what kind of stove did you run in the past? Hows your draft, tell us about your set up (chimney etc....).
Most of the time my stove is humming right along with the front draft control 75% or more closed between 450-600 (depending on the temps outside and size of the load.)
Leaving the front draft control wide open for any length of time will over fire it.
You should be able to take that Oslo up to 600 no problem (assuming proper stove operation, dry wood and good draft)
WoodButcher
Most of the time my stove is humming right along with the front draft control 75% or more closed between 450-600 (depending on the temps outside and size of the load.)
Leaving the front draft control wide open for any length of time will over fire it.
You should be able to take that Oslo up to 600 no problem (assuming proper stove operation, dry wood and good draft)
WoodButcher