InternalError: too much recursion

Using Firefox, right after selecting it from the file picker:

Uncaught (in promise) InternalError: too much recursion
    getPDFSignatureCount utils.js:141
    _updateNeedsPlacementStatus dbp-signature-lit-element.js:421
    queueFile dbp-official-signature-pdf-upload.js:126
    onFileSelected dbp-signature-lit-element.js:472
    handleEvent parts.js:462
    __boundHandleEvent parts.js:428
    sendFileEvent file-source.js:262
    handleFiles file-source.js:243
    zt utils.js:268
    handleFiles file-source.js:219
    handleChange file-source.js:201
    connectedCallback file-source.js:152
    promise callback*connectedCallback file-source.js:140
    __insert parts.js:227
    __commitNode parts.js:234
    __commitTemplateResult parts.js:269
    commit parts.js:209
    render render.js:41
    render shady-render.js:250
    render ScopedElementsMixin.js:141
    update lit-element.js:225
    update base-element.js:43
    update dbp-official-signature-pdf-upload.js:282
    performUpdate updating-element.js:555
    _enqueueUpdate updating-element.js:508
    requestUpdateInternal updating-element.js:474
    initialize updating-element.js:326
    initialize lit-element.js:150
    Qe updating-element.js:90
    st lit-element.js:82
    en adapter-lit-element.js:5
    tn dbp-lit-element.js:4
    BaseLitElement base-element.js:4
    DBPSignatureLitElement dbp-signature-lit-element.js:8
    <anonymous> ScopedElementsMixin.js:120
    B dbp-official-signature-pdf-upload.js:25
    Ft utils.js:110
    <anonymous> dbp-official-signature-pdf-upload.js:652
utils.js:141:20