This post is for Helix Ultimate Version: 2.1.2, SPPB Version: 5.5.2, Joomla Version: 5.2.4, no Template is used.
After updating SPPB to v5.5.2 the right Testimonial Carousel arrow is not visible anymore. I tested this on two live sides and on my local Webspace. With SPPB v5.5.1 the right arrow is still visible.
SPPB v5.5.1: https://i.imgur.com/g9smbHz.png
SPPB v5.5.2: https://i.imgur.com/oDSgbhK.png