Dictation and spinning blue circle problem

I'm having major problems with dictation on my iPhone 5S.

Sometimes after I press the mic input, I get the tones and then immediately it drops out of dictation mode before I've said a thing.

Sometimes, I'm halfway into dictating something, and the dictation freezes, followed by the blue circle spinning for at least a minute after the last letter of text, then it just stops working, and I have to manually quit.

Sometimes, it completely gets lines of text wrong, so I stop dictation so I can correct them, and then some of the badly mangled words change to the correct words. Sometimes they don't. If I insert an edit point too quickly after stopping to correct, it won't auto correct. So I never know how long to wait and see what will happen. If it knows the correct words, why is it making up the wrong ones (often completely unrelated to the word I've spoken, especially when there's often no contextual relevance to the rest of the sentence)?

Sometimes, I'm halfway through a dictation and it drops out of dictation for no apparent reason, but gives me no sign of it otherwise than it just stops taking dictation. Because it sometimes lags behind my voice anyway for no apparent reason, I don't always know when this has happened, since the sine wave indicating it's receiving my input is still responding.

Is this common? Or is there something wrong with my phone?