I upgraded a couple of months ago from an FR 255 to an FR 265. I use an HRM-Pro and a Tempe, along with my Shokz OpenRun headphones, and never had any problems with this on the 255.
With the 265 I have been experiencing dropouts on the headphones, which crashed Spotify and meant I lost my position in podcasts, very frustrating. This morning I thought I would try a run without the Tempe and everything worked perfectly, so I am wondering if the problem is actually with the ability of the 265 to support multiple accessories compared with the 255.
Does anyone have similar experiences? For now I will run without the Tempe to see if the issue is resolved on future runs, but I would really like the watch to support 3 accessories if that's the problem.