Director of rugby Kevin Squire saw his Barnstaple team produce their best rugby of the season for 20 minutes at Chippenham – then it all went wrong.
Barum took a 10-0 lead in the National Three south west clash on Saturday but ended up losing 46-27.
Will Topps (two) and Linford Brock scored tries, to add to an early penalty try, and Luke Berry kicked a penalty and two conversions, but Barnstaple slipped to a fourth successive defeat.
Squire said: "We started off brilliantly and in the first 20 minutes played the best rugby we have played all season. Then, for some reason, it all went wrong.
"Chippenham managed to slow the game down, bullied us up front and were well worth the win in the end. The scoreline flattered them but they were better than us.
"Our defence was shocking all over the park – the forwards and backs were equally as bad."
Barnstaple face one of the biggest dates on their calendar on Saturday when Exmouth go to Pottington Road. The third-placed visitors have won the last three meetings between the Devon rivals.