Can't comment on what's causing the issue or how their stuff behaves, but I wouldn't worry about it too much. Maybe it'll let you buy more at the old price even

The execution thing I mentioned is only a dealbreaker if you semi-actively trade.
What US equities are available for buying on EE at the moment?
They do not have much, but they do have some of the more important companies I personally would invest in for the long term.
Some bigger names they have are 3M, Adobe, AMD, Google Alphabet, Amazon, American Airlines, American Express, AIG, Apple AT&T, Bank of America, Boeing, Broadcom, CAT, Chevron, Cisco, City Group, Coca-Cola, Colgate-Palmolive, Comcast, Costco, eBay, Facebook, Fedex, Ford, General Electric, GM, Hasbro, The Home Depot, Intel, IBM, Johnson & Johnson, KraftHeinz, Mastercard, MacDonalds, Microsoft, Netflix, Nike, NVidea, Paypal, Pepsico, Pfizer, Philip Morris, Snap Inc, Star Bucks, Symantec, Target, Tesla, Texas Instruments, Time Warner, T-Mobile, Twitter, 21st Century Fox, Unilever, UPS, Verizon, Viacom, Visa, Vodafone, Walmart, Walt Disney and Western Digital - just to mention a few.
Then there is also a bunch of ETFs to invest in offered by companies such as BlackRock and Vanguard.
I think, for now there is a decent package available to invest in.