Goodafternoon,
I also get these problems with 4.4.
Maybe there is something wrong with 'gentle' transition from: the Deprecated function USING PERIODIC COMMIT to CALL {SUBQUERY} IN TRANSACTIONS see*.
For me it worked to transform to statement to
LOAD CSV WITH HEADERS FROM 'filexyz' AS row
CALL {
WITH row
MERGE ...... etc
} IN TRANSACTIONS
;
This will periodic commit 1000 lines a time.
To change this use
} IN TRANSACTIONS OF 15000 ROWS
;
Yours kindly Omer
*
Deprecations, additions, and compatibility - Cypher Manual