About burst size of S1 SLC products

I have encountered with a problem I have never heard of. I was coregistrating some S1A and S1B products when I discovered that in some products of S1A the last bursts pertaining to subswaths 2 and 3 are much larger than the others.

IW1: 10 bursts
IW2: 9 bursts
IW3: 9 bursts

I attach some screenshots.

The products which are affected are located in the Orbit103:

S1A_IW_SLC__1SDV_20200102T180208_20200102T180236_030625_03824B_85D4.zip
S1A_IW_SLC__1SDV_20200102T180233_20200102T180300_030625_03824B_44DD.zip

S1A_IW_SLC__1SDV_20200114T180207_20200114T180235_030800_03886B_83D3.zip
S1A_IW_SLC__1SDV_20200114T180233_20200114T180300_030800_03886B_6BC9.zip

S1A_IW_SLC__1SDV_20200126T180207_20200126T180235_030975_038E95_D436.zip
S1A_IW_SLC__1SDV_20200126T180233_20200126T180300_030975_038E95_71D3.zip

S1B_IW_SLC__1SDV_20200108T180143_20200108T180210_019729_0254D5_C5B0.zip
S1B_IW_SLC__1SDV_20200120T180143_20200120T180210_019904_025A67_512B.zip

Bests regards,
M.B