When long pressing on the heart button to react to a post, it starts to highlight something.
A video to clarify:
Could be related to
this.
「いいね!」 4
Lilly
(Lillian Louis)
2
yea it’s doing something similar on my ipad 
「いいね!」 6
saquetim
(Sérgio Saquetim)
5
This issue should be addressed by:
「いいね!」 6
Lilly
(Lillian Louis)
6
excellent - the long tap is working perfect now! nice work 
「いいね!」 3