You are right, that is due to lack of memory. The framebuffer of the MiniGrafx library consumes a big part of the the RAM. The SSL library then tries to allocate nearly 20KB of memory which is not available and the ESP crashes. I tried to work around that by temporarily reducing the bit depth (=available number of colors) to black and white during the update. But I guess embedded systems are not so happy with allocation and de-allocation of a lot of memory so it didn't really work. Do you have a better idea?