[#0] WARNING:Minization -- RooFitGlue: Minimized function ha

dear experts,
I am experiencing some warning issues when running the Histfactory tool to generate the Roofit/Roostat workspace. The Minimisation converges successfully, nevertheless I am wondering whether these warnings should be taken as some serious issue with the tool?
I checked that my input histogram templates do not have negative bins which would last into negative pdf. I explicitely set these bins to zero if so.
Is there something i could do in order to investigate this further? Change the range for the different parameters of the fit, etc…
thanks in advance for any hint which would help.