Yes I agree, a very reduced limited codepen example showing what your seeing, since it will be impossible to replicate this without knowing how to replicate this with the exact dynamic SVG code your trying to animate.
And when you say old versions, what do you mean, old versions of jQuery, since i didnt read anything on exactly what in the GSAP API your having an issue with. But only a mention of you using jQuery.parents().
That looks like this is happening due to the browser thinking the SVG element has no parent. That would throw that ownerSVGElement is null error, especially if the outermost SVG doesn't exist yet or is not part of the render tree. That is why it throws null. You could try and add a setTimeout() or use GSAP delayedCall() to try and get ownerSVGElement after 300ms-500ms and see if ownerSVGElement returns an element and not null. (Giving time for your dynamic inline SVG to be inserted in the DOM)
Firefox has several bugs for this, but we wont know without testing live in the browser with the code your seeing this with.
But a codepen example will help us replicate this, which is the only way to resolve this, so we have some context to test what your seeing.