Tango - unsure if you have addressed these, I think so, so bear with me.
- Chase has acknowledged that they processed the check
- Chase has stated that they know what account the check was deposited in
- Has Chase indicated that the deposited account is not what is on the check?
- Has Chase indicated that the last name and/or address on the account belongs to the LL?
Once item #2 is confirmed; the LL should have been able to get #3 and #4 from Chase .
Chase should be able to provide you a Yes/No on #3.
- If Yes, that is then between Chase and the LL for Chase accepting and processing the check incorrectly based on the account # on the back of the check.
- If No; LL got the funds into his account - case closed
I do not think Chase will release #4 information to you without the LL being there (authorization to release personal info) Again that is between Chase and the LL.
LL may be stating that Chase wants you there because it is your check and your funds that were "mis-handled"
Previously, HSBC was tossed into the mix - where did that happen?

You have account with Citi
LL has account with Chase