Reproducible behavior with the following simplified query [1]
Avoiding the error by including non-restricting criteria on tables not represented in the WHERE EXISTS clause [2].

ie: there seems to be a problem in the Optimization that writing the query similar to [2] will avoid.

[1]
SELECT
'X' as CMR_BPR_ID2
FROM
Y93
INNER JOIN
AG5
ON
1 = 1
LEFT OUTER JOIN
MFSMFL.I58 as I58
ON
1 = 1
WHERE EXISTS
(SELECT 'Y' FROM BH0 WHERE AG5.CONSENT_CLIENT_ID = 1 AND
Y93.CMR_BPR_ID2 = 1 )

[2]
SELECT
'X' as CMR_BPR_ID2
FROM
Y93
INNER JOIN
AG5
ON
1 = 1
LEFT OUTER JOIN
MFSMFL.I58 as I58
ON
1 = 1
WHERE EXISTS
(SELECT 'Y' FROM BH0 WHERE AG5.CONSENT_CLIENT_ID = 1 AND
Y93.CMR_BPR_ID2 = 1 AND
I58.FUND_CODE like '%')