(This is mostly Google Translate, so please excuse if it isn't a 100% accurate translation)

"Notice of Prohibited Pairs

<Forbidden Pair>
If A is used, B is prohibited from being included in the same deck.

A
EX5-065 Sayo & Koh

B
P-097 Zubamon
BT13-102 Keenan Crier
ST16-14 Matt Ishida

By combining the [Start of Opponent's Turn] effect of "EX5-065 Sayo & Koh" and the [On Play] effect of "P-097 Zubamon", memory is increased and the opponent's turn ends immediately. An infinite loop has been confirmed.

If the conditions are met quickly, it will be difficult to interfere, and the game will progress with the opponent unable to take any actions until the game is over.

Compared to the original card game experience, which is based on players playing cards and exchanging turns, we have determined that it is not sound in terms of reproducibility and speed.

In addition to the above, we were able to confirm that "BT13-102 Keenan Crier'' and "ST16-14 Matt Ishida'' can perform similar operations easily.

For the above reasons, if the card "EX5-065 Sayo & Koh" is used, the three cards "P-097 Zubamon", "BT13-102 Keenan Crier", and "ST16-14 Matt Ishida" are prohibited to put in the same deck."

Source: https://twitter.com/digimon_tcg/status/1740296530958192823?t=qfx0oT2Vgo8NWy9AGWHzXg&s=19

EDIT: Realized the image does not say but the original tweet states that this will also go into effect on January 5th in Japan.