TaskRejectedError on page rendering with a vague reason

[silentmantra]

hi, anybody help? the code seems straightforward, the document is opened fine, but rendering rejects with 'Task rejected' message.
Since no specific reason I have no clue how to proceed, happens on any PDF document

    toPromise() {
        if (!this._promise) {
            this._promise = new Promise( (resolve, reject) => {
                this.wait( (result) => resolve(result), (error) => {
                    if (error.type === "abort") {
                        reject(new TaskAbortedError(error.reason));
                    } else {
                        reject(new TaskRejectedError(error.reason)); // here
                    }
                }
                );
            }
            );
        }
        return this._promise;
    }

async function initEngine() {

    const path = (await import('@embedpdf/pdfium/pdfium.wasm?url')).default as string;

    const wasmUrl = new URL(path, window.location.origin).toString();

    const { createPdfiumEngine } = await import('@embedpdf/engines/pdfium-worker-engine');
    return createPdfiumEngine(wasmUrl, {
        //encoderPoolSize: 4,
    });
}

        this.engine = await initEngine();

        const openTask = this.engine.openDocumentBuffer({ id: this.id, content: this.data });
        this.document = await openTask.toPromise();

... child page class:

            const task = this.item.engine.renderPage(this.item.document, this.item.document.pages[this.idx]);

            const blob = await task.toPromise(); // rejects

[silentmantra]

the payload was proxied, no structure cloning was possible