Our buyers did this, sat on things for 6 months and then a week before the agreed exchange date decided to do a full structural survey with drains videos etc
As predicted, then tried to negotiate a price reduction for ridiculous things like the strength of the bathroom ventilation fan. It was a 100yr + victorian terrace that we had fully gutted, rewired and replaced the heating, roof and windows 2 years prior.
By that point the vendor of our purchase was ready to pull out so we said if we’re losing our house anyway- then we’re not selling to you. This was in 2021 so the market was great and we’d had a lot of interest which made this a real threat. Thankfully they saw sense. Our solicitor also pointed out that had we agreed to lower the price, the buyers would have to agree a new mortgage, which would take time, so we would be risking our purchase property anyway, and also losing cash on our sale.
It was honestly one of the most stressful times, but we stood our ground and it all worked out. They paid the offer price we had accepted.
I would assume your buyers are also trying their luck, they either want the property or they don’t. To have paid for a solicitor and I assume by this point- all the search fees, land registry and mortgage arrangement cost. They’re invested so you’re probably safe to stand your ground and reject any price drops for all but a very serious issue.
edited for typos