The term woodland key habitat (WKH) was launched in Sweden in 1990. Definitions for the concept have changed over the years, and today the WKH concept and its application are issues of debate in Sweden. Consequently, the Swedish Forestry Agency (SFA) initiated a collaborative process including forest stakeholders with the purpose to clarify the application and develop the inventory methodology of WKH. We have studied, by means of interviews and observations, participant perceptions of how endogenous and exogenous factors affect the collaborative process. During our research, we identified three game changers: the pause in WKH registration in northwestern Sweden that caused several participants to drop out of the process; budget allocations for new nationwide WKH inventories that put the process on hold; and formal instructions from the government that came nine months later and essentially re-initiated the collaborative process. Altogether, this not only affected the participants’ abilities, understanding and willingness to participate, but also the overall legitimacy of the process – indicating the difficulty of conducting policy development in collaborative form, especially when it is highly politicized since it impact on the participants’ anticipation of the process and its end results.