ORA-0070 database pg_link does not support some function in this context?

Question

PostgreSQL

Good day!

When making a request:

UPDATE "public"."education_salary"@PG_LINK s
SET  "stuff_type"='Все учреждения', 
     "val_salary_03"=2
WHERE "report_date" = '01-OCT-2015' and
      "report_org" = 'ГОБУ НПО ВО "ПЛ № 2"'

result:

database pg_link does not support some function in this context.

Wherein:

select *
from  "public"."education_salary"@PG_LINK
where  "report_date" = '01-OCT-2015' and
"report_org" =  'ГОБУ НПО ВО "ПЛ № 2"'

performed without issue.

If you do:

UPDATE "public"."education_salary"@PG_LINK s
SET  "stuff_type"='Все учреждения', 
     "val_salary_03"=2
WHERE "report_date" = '01-OCT-2015'

All OK.

If the additional condition is to put numerical values, then everything is also ok.
The problem is only in varchar (varchar2) - this is from oracle, in pg this column is "character varying".
Am I fooling myself into the dark? Where is wrong?