Bubble Trouble

I am relatively knew to bread making and have been working mostly with high-hydration, no-knead type breads. The last two breads I have baked in a covered Sitram saucier have had multiple bubbles or blisters in the top surface which I have not gotten before in other baking pans. This last loaf pictured here was an 80% hydration recipe with 2 1/2 cups KA all-purpose, 1/4 cup rye and 1/4 cup whole wheat at 450°. The bubbles had appeared as early as when I first looked in the pan at 20 minutes. In the pictures below, the bubbles can be seen in the first and the crumb on the second. (The crumb picture is a mess because the loaf was stuck to the pan and I had to tear it to get it out.)

I am wondering if this could be a result of the type of pan I used? I thought perhaps it's overproofing but the crumb looks pretty good and the proof rise was only about three hours. Is this just a normal happening in this type of baking? Thanks in advance for any help.

Jessica