The tension between two people who are clearly attracted to each other but are doing their best to keep things within the boundaries of friendship will always be louder than any actual flirting.
Hey so 7x04, 8x11, 9x12 and 9x13 are the only recent episodes along with 10x04 that have a Buck and Eddie solo plot in the synopsis. In case anyone was wondering.
knowing what we know thanks to the synopsis, its most likely hen and chim looking at buddie across the firehouse being mad or wtv (we know this is from ep4)