Rewrite but Cinemasins reacts to every bit:

Narrator (Michael Brandon): Thomas and The Billboard. Knapford is the biggest station on the Island of Sodor. All the engines love its bustling busyness. Today was a very special day. It was Knapford Station's birthday, and there was going to be a grand party. All the engines were very excited. They were to have their photograph taken. The photograph was going to be put up at Knapford on a billboard. Thomas felt very proud.
Thomas: I've never been on a billboard before.
Narrator (Michael Brandon): But the photographer was having trouble fitting all the engines into the photograph.
Photographer: Uh move back there, James. And you forward Percy. That's good, that's good. And Diesel, can you move in?
Narrator (Michael Brandon): Diesel moved in. The camera flashed. Thomas didn't know that Diesel had rolled right in front of him. And neither did Diesel. Thomas puffed into Maron station to pick up the new billboard. He was very excited. But when Thomas saw it, he was very disappointed.
Thomas: Diesel's right in front of me. (Narrator (Michael Brandon): Thomas thought sadly.) No one can see me at all.
Narrator (Michael Brandon): Thomas puffed towards Knapford.
Thomas: Diesel moved in front of me on purpose. (Narrator (Michael Brandon): Puffed Thomas to himself.)
Narrator (Michael Brandon): Thomas felt cross. He wasn't looking where was going. Then there was trouble. There was a cow on the line. Thomas turned quickly into a siding just in time. He hit the buffers, and the billboard flew...into the lake! Thomas went to tell the photographer what had happened.
Photographer: Don't worry. I'll take another photograph. Tell all the engines to meet me at Tidmouth sheds.
Narrator (Michael Brandon): Thomas was about to set off. Then he saw Diesel. Thomas knew he should tell diesel about the new photograph. But Thomas was worried.
Thomas: What if Diesel spoils this one too? (Narrator (Michael Brandon): Thought Thomas.)
Narrator (Michael Brandon): So Thomas didn't tell Diesel. Soon, all the engines except Diesel were back at Tidmouth. Gordon was cross.
Gordon: Mr. Giggles (the famous clown) is coming to the party tonight. I must collect him from the airport. I must not be late.
Emily: And I have to pick up the brass band from Brendam docks.
James: And I have to collect the bunting and decorations from Wellsworth.
Thomas: Oh, okay. I'll fetch the photographer right away.
Narrator (Michael Brandon): Thomas was steaming to Maron. Then he saw Diesel. Diesel was puffing straight to Tidmouth. Thomas was worried. Now Diesel would find out about the new photograph. So Thomas turned onto a branch line, and he raced back to Tidmouth.
Thomas: There's been a mistake. You'll all have to come back later.
Narrator (Michael Brandon): The engines were very cross. Soon they had all gone, and Diesel trundled straight by. Later, Thomas had gathered the engines again. Then Thomas went to Maron to collect the photographer. Just as the photographer was climbing on board, Thomas saw Diesel. Now Diesel would see the photographer, and he would find out about the new photograph. So Thomas wheeshed lots of steam. It billowed from his boiler and filled the whole station. So Diesel didn't see the photographer, and he trundled straight by.
Photographer: The steam has made my camera wet.
Thomas: I'm sorry, sir.
Photographer: We'll have to wait for it to dry. Tell the engines to come back later to Tidmouth.
Narrator (Michael Brandon): So all the engines came back later instead of doing their jobs. At last the photographer was ready. No one had noticed Diesel wasn't there. Thomas was very relieved. But just then, Diesel oiled round the bend. Diesel was surprised to see all the engines. He screeched to a halt. Rolls of bunting went everywhere.
Diesel: No one told me there was another photograph.
Photographer: But I asked Thomas to tell everyone.
Narrator (Michael Brandon): All the engines looked at Thomas. Thomas felt terrible. Sir Topham Hatt was very cross.
Sir Topham Hatt: Gordon, you were meant to pick up Mr. Giggles (the famous clown). Emily, you were meant to pick up the brass band. And James, you were meant to pick up the bunting and decorations. None of you arrived. So Diesel had to do all your jobs, and now he is late to do his own work.
Narrator (Michael Brandon): Thomas was very upset.
Thomas: It's all my fault, sir. I didn't want Diesel to know about the new photograph. In the last one, he moved right in front of me on purpose.
Diesel: I did not. The photographer told me to move.
Photographer: I did. Perhaps you rolled too far.
Narrator (Michael Brandon): Thomas knew then he'd made a mistake.
Thomas: I'm sorry Diesel. I was wrong to think you did it on purpose. And I'm very sorry for causing all this trouble, sir.
Narrator (Michael Brandon): Soon all the engines were lined up. The new photograph was taken.
Thomas: Sir, if I do all Diesel's jobs, can he collect the new billboard?
Sir Topham Hatt: That's a wonderful idea, Thomas.
Narrator (Michael Brandon): Diesel agreed. For the rest of the day, Thomas worked hard. He did all Diesel's jobs. And Diesel picked up the new billboard just in time for the celebrations. It was a wonderful party. There were clowns and a brass band. Diesel and Thomas agreed that the new billboard was the best billboard they'd ever seen.