There is no specific statutory restriction the board obtaining a loan. However, the association board has a fiduciary duty to the members, and the failure to act upon well-informed business judgment creates individual liability for damages
caused to association members. See Caprer v. Nussbaum
, 36 AD 3d 176, 189 (2006).
If the board actions are generating unnecessary costs to the members, any member as an individual, or a group of members could sue the board for the breach of fiduciary and attempt to obtain damages from the board members as individuals. However, the damages would be payable to the association as a whole, not to the individuals who would bring the lawsuit. So, you could not directly recover your additional assessment fees. You would increase the net value of the association assets, and thereby, hopefully, reduce the assessment fees for everyone.
It seems to me that based upon how you describe the circumstances, the board appears to have borrowed this money for no particular reason, and it's costing everyone a small fortune to maintain the interest. All of which argues to payoff the loan and eliminate the debt (or, build the treatment plan).
You will need a competent lawyer, but perhaps you could settle the matter without legal action, and save litigation fees.
For a competent civil litigation attorney referral, see this link.
Please let me know if I can be of further assistance.