1
nonsense --> also nonsense
this block has unreadable times

2
00:00:03,000 --> 00:00:05,000
this one is fine

a block with no arrow at all

3
00:00:05,000 --> 
this one has no end time

4
 --> 00:00:09,000
this one has no start time

5
00:00:09,000 --> 00:00:11,000