Drop frames on the input side DeckLink Quad 2

We capturing data from DeckLink Quad 2 card together with FFmpeg. But sometimes we can see a frames dropping. Please see the FFmpeg log:

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[decklink @ 0x3173f40] Frame received (#325327) - No input signal detected - Frames dropped 3x
[decklink @ 0x3173f40] Frame received (#325333) - Input returned - Frames dropped 4speed=   1x
[decklink @ 0x3173f40] Frame received (#476213) - No input signal detected - Frames dropped 5x
[decklink @ 0x3173f40] Frame received (#476221) - Input returned - Frames dropped 6speed=   1x
[decklink @ 0x3173f40] Frame received (#523472) - No input signal detected - Frames dropped 7x
[decklink @ 0x3173f40] Frame received (#523478) - Input returned - Frames dropped 8speed=   1x
[decklink @ 0x3173f40] Frame received (#530557) - No input signal detected - Frames dropped 9x
[decklink @ 0x3173f40] Frame received (#530562) - Input returned - Frames dropped 10peed=   1x
[decklink @ 0x3173f40] Frame received (#556591) - No input signal detected - Frames dropped 11
[decklink @ 0x3173f40] Frame received (#556596) - Input returned - Frames dropped 12
[decklink @ 0x3173f40] Frame received (#571405) - No input signal detected - Frames dropped 13
[decklink @ 0x3173f40] Frame received (#571411) - Input returned - Frames dropped 14


Visually we have seen a color bar for a moment when frames dropped. This issue doesn't have a stable periodicity: it can occurs 1 time per hour and 1 time per 10 seconds also.
I tried the following FFmpeg command to exclude any encoding, network or discs recording issues:

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ffmpeg -y -r 25000/1000 -f decklink -format_code Hi50 -duplex_mode half -i "DeckLink Quad (4)" -c copy -f mpegts /dev/null

It's only getting data from DeckLink and route it to /dev/null and I still see the same frames dropping issue. The input is 1080i. We using the latest driver and SDK (10.9.5) and the latest FFmpeg version (3.3.3). This server not loaded with others heavy processes, we also tried catch a data in full duplex mode and got the same issue.

Please also see the server configuration:
Motherboard: Supermicro X10SRW-F
RAM 16GB: DIMM Synchronous 2133 MHz (0.5 ns) X4
CPU: Intel(R) Xeon(R) CPU E5-1650 v3 @ 3.50GHz X2
OS: Ubuntu 14.04

Can it be a problem with the DeckLink card? Any suggestion and recommendations will be helpful.