I sort of expected the memory overflow. In continuous mode, you have to read fast enough so that all samples are read before the next acquisition starts. You can play around with the number of samples since this affects the time for an acquisition. You can switch to finite sample mode though you will lose some data but this is how a scope set for s single acquisition works. I never use express VIs and these are probably using considerable time. The best solution would be to use s producer/consumer architecture. This method is shown in the templates.