The drafting of amendments is a good place to start if you want to derail the process. The Articles of Confederation could only be amended unanimously, which was difficult enough without considering that Rhode Island was often obstructionist and several states rarely sent representatives. As a consequence, the Federalists, meaning those in favor of the new constitution, feared that the state legislatures would take the debate on ratification as an opportunity to demand amendments that had previously been impossible to implement under the Articles. The state delegations had done a significant amount of wheeling and dealing at the Constitutional Convention to make the constitution as palatable as possible for all the states, but the state legislatures weren't necessarily fully aware of all the compromises that had already been made and as such might reignite debates that had already been settled. My understanding is that Pennsylvania, Massachusetts, New Hampshire, Virginia, New York, and North Carolina all ratified under the condition that certain amendments be made following ratification. That partly happened because the Federalists successfully argued via the press that the details could be hashed out after the fact, but had a few states not been convinced, then things start to get more complicated. Not only would another convention potentially be needed, but states that had previously ratified would need to redebate and ratify the amended version. Instead of the roughly one year it took in OTL, this process might drag on for several. George Washington, viewed as a symbol of solidarity among the states, hadn't been thrilled about attending the first convention despite supporting it and may not attend the second. That could very well sap it of some of its legitimacy. Additionally, since Washington's not getting any younger, he may be more reluctant to accept the presidency if it's offered a few years later than OTL. Having Adams or Jefferson or some other alternative at the helm is going to create a very different tone for the early days of whatever union follows.