Hello, Captain!

The reported case cannot be classified as a bug since this is a part of the regular gameplay. Please refer to this article, it can help you to solve the issue. Meanwhile, I have moved your topic to Game Discussion thread.

@daranmoghadam Without seing the report, it's hard to comment, but some of the common mistakes that players do in this regard:

a) hitting an "adventure" instead of a prize ("adventures" are about 4 times harder),

b) hitting off prize with def units or def prize with off units.

You can be certain that you did not hit a level 7 Prize - It must have been a level 7 Adventure (shown with a gold crown) - http://prntscr.com/i0yslf

Check your lighthouse and battle reports - This adventure will kill 63,420 strength and gives Brethren Units as reward
Brethren Juggs from offense adventure (red) and Brethren Subs from defense (green)

daranmoghadam said:

All my pirates are dead on a low level attack, it took my dread fleet on a level 7 attack WTF, how can I do a 37 level then, tell me?

As others have written, you hit an adventure and not a level 7 LH target. You posting a level 37 LH kill is a dead give away on what happened.

Always use Quests "Riches and Glory" to see where you really are in the game and to pick up other small awards for each higher level that you hit.

Icy said:

As the others said its probably an adventure. But why are you using dreads on prizes? 

It makes perfectly good sense to send dreads .... if you know what you are doing

I send one of EVERY unit type to prizes, but not adventures

.... but things can go badly wrong if you are too ambitious :)

Level 22 Caravel - https://prnt.sc/8g0k68

Always send a few extra marauders if in doubt