FF slow after 2 hour time mark

[dslowik]

I've been running version 3.6.6 for quite awhile with no problems, but noticed a problem this weekend when fast forwarding through a 3.5 hour recording. Anytime that I either FF past the 2 hour mark or watched it past 2 hours and then FF, it took what seemed to be a minute to resume playing at the new location. I upgrade to 3.7.7 and it made no difference. The program was recorded on with NPVR using a HDHR4-2US . I attached logs.
In these logs I did the following.

Started NPVR and the show College Football_20160903_19002230.ts
21:43:22 skip 35 minutes
21:44:07 skip 35 minutes
21:44:50 skip 35 minutes
21:45:14 skip 35 minutes
It was roughly a minute before it started playing again. All other skipping jumped to the correct location and started playing immediately.

[sub]

How big is the file on disk?

[Graham]

How big is the file on disk?

And is the file badly fragmented? Perhaps, the disk is quite near capacity forcing the file to be fragmented.

[dslowik]

How big is the file on disk?

The file is 21.5GB.
The drive has 973GB free and 1.8TB used and reports back 1% fragmentation.