First-half tries from winger Steve Slingsby and flanker Laurence Cowen provided little comfort as Ionians were 36-20 behind with half an hour left to play.
But late tries from second row Joe Makin and No 8 Ed Falkingham saw them snatch both losing bonus and four-try bonus points.
Wharfedale slipped closer to relegation after a 30-10 defeat at Plymotuh Albion. They were a match for their high-flying hosts in the early stages, with a Philip Woodhead try and five points from James Guy keeping them close at 10-10 before the Devonians pulled away.
Harrogate ran out 23-15 winners over Broadstreet in National Two North. Tries from Noel Minikin and Jake Brady were added to by Lewis Minikin, who kicked a conversion and three penalties.
Ten points behind with half an hour on the clock, Sandal fought back to beat South Leicester 29-20.
Two tries from flanker James Briscoe and one from second row James Stewart were added to by stand-off and captain Greg Wood who kicked a conversion and four penalties.
Otley were beaten 27-19 by promotion-chasing Stourbridge, while bottom of the table Huddersfield lost out 22-12 to visitors Caldy.
National Three North champions Sheffield Tigers maintained their 20-point lead over Wirral despite being held to a modest 17-15 margin in their home win against Hull.
With the title already in the bag, Tigers had to be focused as they played their part in a very physical game that saw Ed Simmons and Henry Packard score the tries.
Mark Ireland played his part, converting twice and slotting over a penalty.
Sheffield slipped a place to fourth when they were handed a 41-19 beating at Rossendale.
Ilkley recorded a 13-10 win at Waterloo, while Cleckheaton also won on the road, beating Birkenhead Park 22-17. But Huddersfield YMCA were narrowly beaten 26-23 by visitors Billingham.
West Leeds booked their place in the RFU Senior Vase final at Twickenham when they beat Oundle 31-23, with tries coming from Kier Breakwell, Mark Calderwood and James Damarell, while Dale Breakwell kicked two conversions and four penalties.
Unbeaten for 57 consecutive matches, Wetherby lost out 13-7 to Buxton in the semi-final of the RFU Junior Vase.
Doncaster Phoenix put the North One East title beyond Morley’s reach with an eight-try, 50-17 home victory over Guisborough.
Right winger Lee Wallace ran in a hat-trick of tries, and outside centre Will Burden added two more.
Morley, 18 points adrift but with a game in hand, also scored a bonus in a 40-19 win at Driffield. Morley raced into a 33-0 lead at half-time before holding on to take victory.
Dinnington came from 10-0 down at half-time to scrape a 14-10 home win over Pocklington, reversing an away defeat earlier in the season and swinging the match with a 75th-minute try by full-back Chris Williams.
Wheatley Hills, already 22-10 ahead by half-time, were restricted to a bonus-winning fourth try by lock Andy Penno in the second half but beat tailenders Beverley 29-10 at Doncaster.
Bradford and Bingley maintained a nine-point margin over Malton and Norton at the top of Yorkshire One when they ran in seven tries in a 41-20 victory at North Ribblesdale.
Full-back Benny Greaves scored a hat-trick and right winger Adam Sutcliffe touched down twice. Malton also managed a bonus with four tries but were held to a 24-22 winning margin in a cliffhanger against Scarborough at the Gannock.
Ali Coe scored the winning try for Malton and Norton, while Ben Boothman, Jamie Rounthwaite and Ben Woodhouse also crashed over.
Third-placed Bridlington also kept on the pace with a 38-7 win at Selby with winger William Davies scoring a hat-trick and Gary Stevens two, but second- bottom Old Crossleyans pulled off an upset as they beat fourth-placed Hullensians 33-17. Ryan Sweeney, Chris Vine and Richard Wheal scored their tries.