I also open my base every now and then and drop around 2000 trophies. I do it for several reasons, one of the most important ones is becoming a shield for my lowest team members. I give lot of skulls, so lower plus higher players of opponents that are careless raid me, instead of them. Their attack fails and they have one attack less for attacking my lower members. And there are always players who don’t want to give up, even when it doesn’t make sense to continue. Their hero dies very fast and then they start to resurrect and heavily scroll, just with intention to beat the base. It gives gems, sometimes even more then you will be able to win by tournaments, but don’t count on it.
Try to do the following scenario at the beginning of the recess, enter your name in the open bases topic and open your base and leave some loot for grab. A day later, be polite and tell players that you close your base again after you dropped enough trophies. Be smart and still leave some unprotected gold (a few M would do) You will notice that within a few days your trophy count is almost back to normal and as a reward you probably got some gems. The problem you mention I did not have.
Don’t use matchmaker after losing a lot of trophies, that is useless, those players are only giving you 25 to 34 medals. Just search for alliances in the neighboorhood of your team and raid players somewhere around your old trophy count. Make sure you don’t attack the same player too often, ou don’t want to become a harasser, since stronger Alliance members of that team could go to add you to their favorite list. It’s better to take on players with (war) boosts, if you can handle them, they give most loot plus medals.
Players in favorite list are probably attacked several times by your hero and probably beaten very often. Once you beat a player too often, the medals for that base are lowered, maybe even to 27 like you mention. Maybe something changed with 2.0.0 version, but I didn’t encounter any problems so far. I must admit I also never take any notice of the tournaments. During war season I seem to raid that much that I win some leagues, during recess I drop to lower tournaments, due to lack of raids. I see the winnings as a nice extra, nothing more, nothing less.