I had the same issue. I think it's polar flutter or some kind of distortion. Same with other signals that way. I could see the 5 streams, but only a rare decode when they were stronger.
I had the same issue with FT8WW weeks ago on FT8 but I easily caught him on cw on the same day within hours.
Also the same happened with 9N7AA and JT1CO both on 10 meters ft8 which was a major failure but then after they both moved to CW I easily caught them on 10 meters.
I checked both 9N7AA and JT1CO for the next two weeks on ft8 and all times FT8 failed to complete a contact but when the same stations went to cw they were easily worked.
I had a similar experience with an Armenian and other central asia hams on 20 meters this past week where FT8 beaming over the pole for me failed miserably but cw worked fine.
I'll stick to CW over FT8 after my most recent experiences and yes I know that some of these rare dx hams don't get down to cw much but maybe they need to reconsider this mode and give up on FT8.
FT8 isn't the great weak signal mode that some think it is and so far for me and my hearing and my ears have succeeded at cw when FT8 has been a major failure.