Your internet browser has a set cache limit. When it is reached Mega download stalls. I have the same problem when I start downloading files over 500 mb because I set my Mozilla Firefox cache to 500 mb. If you download the Mega App, then you don't run into that problem. I have it used the app many times and had no issues downloading files bigger than 1.0 gb. I suggest you download and installed the Mega App for free.
Another alternative would be MegaBasterd (it's even better when used with a regularly updated/generated proxy list):
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It needs Java 11 (or greater) to run:
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A good starting point for finding the right proxy list:
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