I have always believed that 'civil asset forfeiture' was unconstitutional.
Fourth Amendment
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
Even with a warrant, to not describe what is to be seized beforehand is a license to steal.
An inanimate object is not capable of committing a crime, in and of itself (just as guns do not kill, the people handling them do), therefore the entire tenuous thread of legal logic by which assets are seized without any proof that they are the proceeds from criminal activity, and on occasion, completely outside a criminal context, violates the 4th Amendment prohibitions on taking the effects of a person.
In this case, suspecting the firm was aiding in laundering or protecting assets of criminals is one thing, but to loot the boxes of all customers without providing a criminal connection is a blatant violation, not only of the terms of the warrant as described in the video, but of the Constitution itself.
A far better course of action would have been to prove criminal activity of the business, and with the records thereof, prove any ties to criminal activity of the individual owners thus connected, while leaving the other box owners out of it.
For a front operation to exist, if it is a front for criminal activity, it would be most successful if at least a portion of the business is legitimate. That way, people who are not criminals are not likely to have suspicion raised if they try to do business with the operation as legitimate customers. The FBI should know that.