I see there is a Q&A regarding descoring caps. https://www.robotevents.com/VRC/2018-2019/QA/173
This is a tricky issue that allows a lot of referee discretion. Unfortunately ref discretion turns into different interpretation from region to region.
A couple of thoughts...
If teams are making a good faith effort to knock caps back into the field using a descore arm, they should be given the same benefit of the doubt as teams trying to score caps on posts. Caps ending outside of the field CAN BE INCIDENTAL and UNINTENTIONAL. It's not always a rule violation if a cap goes out of play.
The same standards should be held for scoring and "descoring" (descoring in this game is actually scoring for your own team and is an offensive action and not purely defensive). If we are going to penalize teams removing caps from posts for an action then we should also remember to penalize teams scoring caps on posts in the same manner.
It's good to remind ourselves that if a team is not trying to keep the cap in the field while removing it from a post then it is a rule violation. Of course a team could get snagged for a rules violation by "repeated" knocking caps out of play, the Q&A seeks to clarify where that limit should be.
<SG8> Keep Game Objects in the field. Though it is expected that some Game Objects may unintentionally leave the field during Match play, Teams may not intentionally or strategically remove Game Objects from the field.
An intent of this rule is to prevent Robots from “knocking” Caps out of the field to remove them from Posts. Any strategic, intentional, or repeated removal of Game Objects from the field would be considered a violation of this rule.
Minor violations of this rule that do not affect the Match will result in a warning. Match Affecting offenses will result in a Disqualification. Teams that receive multiple warnings may also receive a Disqualification at the Head Referee's discretion.