Relationships deteriorated later in 1884, when most of the Cwmorthin workings in the Back Vein collapsed. The ground above the workings was fractured, right up to the top of Allt-fawr, where Llyn Bach, which supplied water to Holland's workings, was drained as a result. The fall had disastrous consequences for Cwmorthin, with production falling from 11,600 tons in 1884 to 6,900 tons in 1886. About half of the mine became inaccessible. In order to develop the quarry further, they had to open new chambers below the level of Llyn Cwmorthin. This was costly, as development work produced little productive slate, and there were additional costs for pumping and for machinery to raise the rock up to the level of the mills. Between 1876 and 1888, 132,866 tons of slate were shipped, but the burden of development was too great, and led to the winding up of the company in 1888.