JD, I have not looked at this closely, so this is all supposition.
Most minesweepers are optimised for slow operations. As you may imagine, speed is useless if in a minefield. So they try to put their ship far from larger ships.
That being said, the simplest answer is the merchant did something that violated the nautical Rules of the Road, or the sweeps bridge watch screwed up.
Since most small vessels know they will lose in a collision, I'd assume it was the sweeps Captain's fault.
"These things must be done delicately-- or you hurt the spell." - The Wicked Witch of the West.
"We've got the torpedo damage temporarily shored up, the fires out and soon will have the ship back on an even keel. But I would suggest, sir, that if you have to take any more torpedoes, you take 'em on the starboard side." Pops Healy, DCA USS Lexington.