Thank you for reaching out to the Samsung community! As you are facing S pen issue only in G board app then it will be the issue of third party application. Kindly contact the G board application support team.
Be sure to hit ♡ when you find an answer that works for you. For further assistance, you can get in touch with us via Live Chat option by following- http://livechat.support.samsung.com/Customer_new/IN. You can also connect us via Samsung Members web community by following mentioned url-https://community.samsungmembers.com/en_IN#/