In X17 beams and posts are now treated as the same framing member category, so group select grabs both by default. To isolate beams you need to switch to the Select Objects tool, open the Select Similar or Filter options, and temporarily limit the selection to the specific object type or layer the beams are on. The reliable workaround is to place beams on their own layer, lock or turn off the posts layer, then use group select so only beams are available to grab. This mimics the old behavior even though the underlying category is now unified.