Dear Hans, 

Here is a small example which shows a strange spacing in the aligned display math mode.
The same code is OK in both inline mode and just display mode, but it is not good in aligned mode.

I hope that it helps your fix .

Thank you.

Best regards,

Dalyoung

%%%%%
running luametatex version 2.03.3,   ConTeXt ver: 2019.12.12, format: 2019.12.14
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\starttext
    
    \startitemize
    \head inline formula:

    $1001 \times 23 \equiv 1  \quad \pmod {3837}$

    \head display mode

    \startformula
    1001 \times 23 \equiv 1  \quad \pmod {3837}
    \stopformula

    \head aligned display mode

    \startformula\startalign[m=2]
        \NC 2^7 \equiv \qquad \NC \pmod {341},  \NC 14^7 \equiv \qquad \NC \pmod {341}, \NR
        \NC 11^7 \equiv \qquad \NC \pmod {341}, \NC 3^7 \equiv \qquad \NC \pmod {341}, \NR
    \stopalign\stopformula

    \startformula\startalign[n=3]
        \NC 1001 \times 23 \NC \equiv 1  \quad \NC\pmod {3837}  \NR
        \NC \qquad \times 23 \NC \equiv \qquad \NC\pmod {3837}  \NR
    \stopalign\stopformula

    \stopitemize
    \stoptext