DST800 flap

[tomsp]

I installed the depth, speed, temp DST800 in March 2017. Boat was back in the water Late June 2017 and has remained so since. When I'm not sailing I remove the transducer and insert the blank. When I sail, 2 days a week, I take out the blank and insert the transducer - in SF Bay leaving the transducer in will see it clog up with critters in no time (less than a week). Removing the transducer and blank have been effortless with very little water ingress. Friday I went sailing - going out for a couple of days- at dock I tried to remove the blank to insert the transducer and the blank was really difficult to take out - when it did come out water really gushed up. Putting in the transducer was difficult too - it did t seem to want to seat correctly and water kept oozing in. I re-set it in the [censored] twice and finally water stopped and all was good. Sunday I removed the transducer- came out easy- but water just gushed in again as if the flapper was not there. Without hauling the boat to check is there a way to see what's happening down there?