I've passed the info on including network traces.

If you are sending multiple contract offers by clicking on a player, then from the player card selecting the offer contract option, the years and requested bonus will be populated with the previous offer you made to any player (not tested if you logout then back in).

WORKAROUND: Drag slider bonus to 0%.

This forces a call to the server and you get a message like this :-

A multi-year offer requires a bonus
This player will not renegotiate for a bonus less than $13,782,447
A 4-year contract must include a signing bonus of at least $197,576

$13,782,447 is the true minimum bonus. Manually enter that into the bonus box.

Testing has shown that this problem ONLY occurs when offering contract through the player card. If you click the player to get the card up then select View to get the full player page displayed, this problem was not observed when selecting offer contract from there.

To calculate the percentage of a number, convert the percentage to a decimal (by dividing by 100) and multiply it by the total number. The core formula is: ({Part} = ({Percentage} \div 100) \times {Whole}). For example, to find 15% of 45, calculate \(0.15 \times 45 = 6.75) (copied from Googley).

bonus min is 10,000,000. year 1 salary must be at least 25%

25 ÷ 100 = .25
10,000,000 x .25 = 2,500,000.
The year 1 salary must be 2.5M or more for a 10M bonus.

Or, one can really mess around with the sliders. The new UI automatically does the math but if one enters the bonus required in the bonus area first (remove commas) the interface will really screw things up and one has to start all over.
Expect to start all over many times.
The new contract system was dramatically and unnecessarily changed in the new UI.

I never used Jsids program, which used 24.99% in it's equation. Jsid's also forced many players into offering 6 yr max contracts, regardless of the players experience, because Jsids program abused and made it easy to abuse the MFN contract bug.

The old system was easier to use and far less time consuming. The new UI takes a ton of user time in a lot of areas that did not take much time in the old UI (especially with player related functions: contracts/draft board/depth chart/player searches blah blah blaaaah).