How long have you had your Bellroy for?
I did the exact same thing and LOVED my Bellroy case. Sadly after 2 weeks one of the corners started to split. I sent it back, no questions asked and then I had my new one for about 3 weeks and both lower corners started to crack. I never dropped my phone and I never took the phone out of the case. The rubber sides simply started to split.
Let me know your experience, if it's better than mine I may give it another go.
This is not good news. I've had mine for 2 months and I'm on my second one. The first one got a crack in the exact same place shown in your picture. I got in touch with them and they overnighted me a new one no questions asked. So far the 2nd one is ok but seeing your post makes me thing it's a design flaw. Oh well.