This is part of the curing process of the adhesive. As the wallpaper adhesive dries, it will begin to tighten and bubbles will disappear after 3-4 days.
It normally takes 3-4 days for the adhesive to cure fully in an ambient temperature of 22 degrees. If there are still bubbles remaining, it may be a result of the adhesive still drying in those areas. Give it a couple of days and they should disappear.
Contact us if you are unsure or if the bubbles are still evident after 2 weeks.