Using the & sign followed by a pause is redundant. Instead, just use the @ sign for the walking command and use “then” on the same line.
&XX1 spot 0.932 148 146 in zone 2 and XX1 faces right and XX1 is idle_shiftweight_neutral_loop
@SERPIA1 walks to spot 0.956 254 129 in zone 2 in 1 and SERPIA1 faces left and SERPIA1 is walk_tray_neutral_loop THEN SERPIA1 faces right and SERPIA1 is tinker_stand_neutral_loop_rear