SSAS tabular only works with Windows authentication. So if the server is indeed in Tabular mode you need to try it that way.

either repeat or use one of the following 2 options.

select *
from (select t1.field1
    , t1.field2
    , (select top 1 otherfield
    ...

hum.... may have misread it initially. @SQL_CODE is what contains all the calls to dbo.elast.... bad design on how it was implemented.

so back to those functions. Not sure which...

@alexandermkd 
the code for proc TARIFF_SIM_MATRIX_3M does not match that of the code being executed as per the explain plans you supplied.

just...

@jeff - the OP has already tried the some trace flags and also had the legacy configuration turned on .
ALTER DATABASE SCOPED CONFIGURATION SET LEGACY_CARDINALITY_ESTIMATION = ON is the...

you can still do it although manually.

look at table XVBS_LOG_3M and identify the offer_id that took the longest (you need to compare each record with the previous one...

you need to install SSDT.

either with shell for vs2017 https://docs.microsoft.com/en-us/sql/ssdt/download-sql-server-data-tools-ssdt?view=sql-server-2017
or 
for vs2012 https://www.microsoft.com/en-us/download/details.aspx?id=36843

do you have the explain plan of the proc that is being executed inside the code of the plans you supplied? TARIFF_SIM_MATRIX_3M is being executed on a loop and 
both...

the issue is that the last line fails to meet the correct delimiter "\"\r\n" and as such the value contains a quote

try changing the table to
create...