There isn't any venting for the washer p-trap at all. Of course it's going to siphon itself dry.
Also, the standpipe is too long which also hurts. The p-trap needs to be on the same floor as the washer, not in the crawl space.
The rubber tee will deform soon and become worthless. It's not a fitting that meets any plumbing code.
I see santees on their back on the horizontal line. Those should have been wye or combo fittings. I hope you didn't pay a plumber to do any of that.
804.1 All plumbing fixtures or other receptors
receiving the discharge of indirect waste pipes shall be
approved for the use proposed and shall be of such
shape and capacity as to prevent splashing or flooding
and shall be located where they are readily accessible
for inspection and cleaning. No standpipe receptor for
any clothes washer shall extend more than thirty (30)
inches (762 mm), nor less than eighteen (18) inches
(457 mm) above its trap. No trap for any clothes
washer standpipe receptor shall be installed below the
floor, but shall be roughed in not less than six (6)
inches (152 mm) and not more than eighteen (18)
inches (457 mm) above the floor.