LoTW downloading QSLs - QSO not found messages

[OH3OJ]

Hello, got interesting problem in our club station (OH3AD / OG70AD) Swisslog, which I have not managed to fix so far.

When downloading / importing the QSLs from LoTW there is error list generated with large number errors based on "QSO not found". 
How ever these QSO are exported from SWL to LoTW and are in both SWL log and LoTW. And as confirmed in LoTW but some how in import process these do not match and are not marked in log as confirmed as the "QSO can not be found".

What should I look for to correct it ?

73's de Jukka. OH3OJ